I've owned a pair of Bose QuietComfort 15 headphones for the last seven years, I chose them as I preferred the over ear design and I liked having a replaceable battery which I could change on the move without the hassle of recharging. The noise cancellation of those was class leading, when new, but has since been left a little behind as newer models have been released.Since 2012, bluetooth wireless has become mainstream. My daily phone (Oneplus 6T) doesn't even have a headphone jack and I had to use an adapter to connect my old headphones. This wasn't a major concern, neither was the wire, as I only really use my headphones with my Google Pixel C tablet when sat still on the train. When moving around I usually use a set of Plantronic earphones, which are more suited to walking and running than a heavy pair of cans.By 2018 I'd worn out one of the two included headphone cables and had ordered my third paid or earpad cushions - I use these headphones every working day a couple of hours. The headphones were visibly as new and fully functional, but some parts simply worn out after some 3500+ hours of use and I suspected the noise cancellation wasn't as good as it used to be.So I started looking around at options. I liked some functions of the Microsoft Surface headphones, but they didn't quite tick all the boxes for me. The Sony headphones were getting great reviews, but would only connect to one device over Bluetooth - given the entry cost of these devices I wanted to make sure I was somewhat "future proof" and a single device seemed a bit limited. I also wanted USB-C charging, which the older Bose headphones didn't have. My phone and tablet are both USB-C so I wasn't going back there.Enter the Bose 700 Noise Cancelling headphones which appeared to tick all the boxes for me:- Bluetooth wireless including "HD Audio: AAC" support.- Touch controls for volume, track skip etc- Class leading noise cancellation including a button to disable temporarily if somebody like cabin crew or train guard need to talk to you momentarily.- 20 hour battery life - well in excess of my tablet and enough to get me over a week between charging.- Google assistant (and Alexa) support. Don't expect to use this much but it's there should be usage change.- High quality phone call options - again, not expecting to use much but a nice to have for many.- Can connect to multiple (two) bluetooth sources concurrently.So I ordered the NC 700 and eagerly awaited delivery.On arrival I took them out of the box and they were exactly how I expected. My old QC-15 only had one switch but these looked much cleaner, especially in the black finish vs the old silver. The new band design is pretty stylish and works well. The size adjustment is different but works well and I find the 700s sit on my head nicely for hours without any discomfort. If you have a larger head, the headphones won't fit back in the case without sliding the band back first - this is fairly easy but I guess could get annoying if you used a lot and were at the larger end of the adjustment. The mechanism is also a little "loose" which, while they won't change size in use at all, may rattle a little if you were walking in them. I don't plan to move around so no concern for me however.I'd read about a LOT of problems with the app needed to set the headphones, but these were largely from early adopters and the app has since been updated, fixing a lot of the issues. Also most of the problems were from Apple iPhone uses, I'm an Android guy. I expect I'll be fine...Seems I spoke too soon. Bose didn't quite get this right. I downloaded the "Bose Music" app easily enough and registered to use - something that shouldn't be necessary. I used my Facebook login to activate the app, rather than having a dedicated username/password for Bose.App fully activated, I turned on the headphone and they were detected right away by the app. So far, so good. Then the app tries to automatically pair the device with your phone. It didn't work. Not much troubleshooting, just said it had failed. Tried again, failed. Being a techie, I then decided to go to my phone's bluetooth settings and pair them manually. I had to turn the headphones off and on again, to get them back into pairing mode and visible on the phone's bluetooth interface, but pairing worked first time. I could then use the Connect button in the app and view all the settings. OK, we're good to go.I put the headphones on and pressed play on some music in Spotify. Worked first time, all good and audio quality (whilst subjective) as good as I expected and no major concern when compared to my old QC-15. I'd heard some concerns about bass levels etc but these are just fine for me - they aren't going to give Beats levels of thumping bass though, thankfully.My phone prompted to finish completion of the Google Assistant function, I tested that and it worked well. You press a dedicated physical button on the headphones for this although I understand you can just say "Alexa" and it will trigger without a button push - may not be useful in public! I was surprised how quietly I could speak and be heard though.I tested different noise cancellation levels and the ability to hold the NC button down when somebody walked up to my desk. This function is great, but a little slow. Somebody walks up and starts to talk, you reach for the button, can't find it right away as they are new, and then when you finally hold down the button it takes about 1.5 secs to mute the music and switch off the noise cancellation. It's quicker to take them off so the feature just misses the mark for me - I may look at reprogramming the button so I can just kill it in one click, but this won't pause the music. Turning the headphones off also won't work as then the external sound will remain muffled, and turning off also takes a second - playing a shutdown chime as it does so. So it's great if you want to talk to somebody else and press the button before doing so, but a bit of hassle if somebody taps you on the shoulder before you see them coming. Maybe this will improve with a future update. The noise cancellation overall is superb though, and a marked improvement on the QC-15. I put this down to newer tech with more microphones and better foam cushioning that works better around my glasses.The touch controls are working very well. Double tap to play/pause, swipe for volume or track skip. So far they work well for me and I haven't had any failed or phantom touches, despite hot, sweaty hands in a heatwave - will update the review if this happens.Battery life is what it said on the box, they arrived with about 4 hours of charge - the battery meter in the app doesn't refresh immediately though which confused me after they'd been on charge a while and it didn't appear to have gone up. I understand a 15 minute charge will give you three hours of listening time, which is good if you forget to charge them and only have a little while before running for your train. I haven't validated the 20 hours of life but I don't expect to be disappointed here. No, you can't use them while connected to the charger, I tried.While testing the music, my phone rang and the headphones immediately alerted me by not only ringing but also telling me who was calling without having to look at my phone. Handy. I answered the call with a double tap and began to talk. The caller had no idea I was on my headphones and I could hear them clearly in a "centre stage" position with noise cancellation meaning I couldn't hear the office noise around me. It led to a very clear, comfortable phone call and it made me realise I'd use them a lot more for this function than expected. I can watch videos on my tablet and, should my phone ring halfway through, I'll be able to take the call without taking off my headphones. Perfect.Which leads me onto the multiple device support. I installed the Bose Music app on my tablet and signed in using the Facebook credentials I'd used last time. It saw my headphones and tried to pair with them, again badly. Being familiar with the process I turned on the headphone, then held down the power button for a second or so until I heard a voice prompt "ready to pair another device". All paired up, I played a video on my tablet. I heard audio, but bad, choppy broken up audio. Like interference you would get with a bad signal, but the devices were next to each other. I tried music on my phone again, all good. Back to my tablet - broken. Totally unusable. I turned everything off and on again. Hold on it's working. Perhaps it was a fluke problem. Then I noticed I hadn't entered my pin code on my phone, when I did it completed booting and the Bose NC 700 announced "Oneplus 6T connected" and the tablet audio died again. I could use one, or the other, but not both - pretty useless given the multiple device support I'd bought them for.A Google search revealed I wasn't alone with this issue and it wasn't limited to Android to tablets. I found a couple of people trying to connect a Macbook as a second device without success. All suffered from the same broken, stuttering audio. I searched some more and found a reference to a firmware update for these headphones. What version was I using? I looked in the app for a reference to it.Open the Bose Music app, find your headphones, turn them on, then use the "Connect" button. Randomly at this point the app will make you go through the "ready to connect another device" function again. I just had to when reproducing the steps for this review. It's now showing battery life as 20hrs 14mins and hadn't finished charging when I turned them on. Once connected tab the picture to go through to the device details and then click the "settings" button". Scroll down the list and towards the bottom is "Technical Info". Tapping this will show the firmware version, manufacturing date etc. I was running 1.0.9.863.47372cb but then it displayed that it was downloading an update. No prompt, no "do you want to update?", it just did it. Music carried on playing during the process but I couldn't stop it.I have no idea where it downloaded the update from but it was sloooow. It took around one hour to complete. Don't turn the headphones off, it will stop and you may have to start again. Don't try it on another device to see if it will go quicker, you'll just have to start again - I did. Just wait.After the wait I had been updated to version 1.1.4.1144.be3bf4b - the headphones had to reboot for this, so music was stopped momentarily. I'n now on the latest version, but did it fix my problem?I tried music from my phone, all good. I tried video on my tablet, audio still broken. I turned off bluetooth on my phone, tablet audio fixed. Phone back on, tablet audio broken. It was better in that I didn't have to reboot to fix the fault each time it happened, but I still couldn't connect two devices at the same time. Should I send them back?One last Google around, I found similar problems people were having with the old Bose QC35 headphones. These had suggested updating the software and then performing a factory reset on the headphones - a process which required a button that doesn't exist on the NC 700. So I searched for a reset procedure for the NC 700 and found one that would clear the Bluetooth settings. Process as follows:Turn the headphones off.On your phone, go into Bluetooth settings and delete the NC 700 headphones.On your tablet and any other devices, go into Bluetooth settings and delete the NC700 headphones.Turn the headphones on, while wearing.Press and hold down the power button for 10+ settings, ignoring other prompts, until you hear "bluetooth device list cleared".Now open the Bose Music App on your phone. Try to connect to your headphones, it will try to pair them again. Mine failed like it did the first time but I tried and tried until is succeeded. DO NOT pair them using your phone settings. Let the app do it. Once successful, do the same on your other device. Now test.Since doing this, my set-up has been flawless. But it took far too long to get to the this point, using the combined knowledge or myself, some forum posts about these headphones, some posts about older headphone and some guess work. But we're working, finally.So, on to the scoring...For £349 these should be five star headphones. In fairness, they probably are, but the software lets them down. I only got these working as I'm a real techie and I refuse to give up - they'll get a lot of faulty returns and rightly so.I've taken a whole star off for the bad app that won't even run in landscape mode on my tablet. The pairing process is a joke and should have been easier - most headphone manufacturers get you to use the device native pairing on your phone or tablet, this would likely have been easier for most owners.The other star I've taken off for a combination of the following:1) Bluetooth audio isn't as high quality as that with a wire. Other wireless technologies exist but aren't supported by this device. The HD audio support also seems to be a bit hit and miss, sometimes the option doesn't appear on my phone/tablet after connecting. The headphones are capable of better quality than the bluetooth connection allows.2) The headphones can't be charged while laying flat in the case.3) You can't use the headphones while connected to the charger - rare use care, but why not?4) The noise cancelling override function takes a little too long to engage.5) The case zipper is too long and it's hard to fully open whilst holding them. Hard to explain, but you'll know the first time you try to open them. The case folds open like a book and the spine isn't long enough.6) Compulsory registration with Bose - should not be needed.7) Software update wasn't automatic and would fix many issues if this happened during first time set-up.8) Switching playback source devices could be easier. If I want to go from music on my phone, to video audio on my tablet, the process is a bit of a fiddle.So, five star headphones with 1.5 stars of niggles. I'd have given these 3.5 stars but, without that option, I gave them a 3 rather than a 4. I'll update this review if any of these things improve. I'm also happy to answer any questions posted to this page if I've missed anything - although can't answer Apple issues.I'm happy with the headphones now, with no plans to return, but they don't justify the entry price until some of these niggles are fixed.