I had been using UE Triple-fi 10s for over five years when, finally, the sound started to go from one channel (and a replacement cable made no difference). Having had such reliable service from the TF10s (when I had previously gone through two pairs of Shures in less than three years) I knew that I wanted to stick with UE, and I really wanted the 900s, but I was put off by the price. I did lots of research into other brands and nearly drove myself crazy trying to decide but, in the end, I knew the indecision was being caused by the fact that I really wanted these.
I'm happy to report that since I received them any misgivings I had about the price have become non-existent. These are fabulous earphones. I have spent the last few days working through my music collection, hearing detail in the songs that I either hadn't noticed before, or hadn't heard in so long that I'd forgotten about them. The sound is crisp, bass punchy, and I have really noticed how well the vocals come through. The soundstage is spacious and really gives the music room to breathe. I was fortunate in that the silicon tips that were on the earphones out of the box are a perfect fit. I briefly tried the Comply tips and another pair of the silicons, but immediately went back to the original ones. The sound isolation is very good indeed, better than the TF10s I find, although I have had to stop myself using them whilst walking along the street as, even with the volume right down, I found I wasn't as aware of my surroundings as I should be. On the tube, though, they are fantastic.
So, excellent earphones. But what I really want to note is Logitech's customer support. The UE 900's come with the blue (mic) cable attached and I was blown away immediately using them as was. But I decided to switch to the black (audio) cable just to check everything was working and immediately noticed a slight bias in the sound towards the left channel. I spent a couple more days listening to this to see if it was my imagination, switched back to the blue cable and found that it wasn't. I contacted Logitech by email and asked them if they had any possible solution, and received a reply within a few hours saying they would send me a new cable without further question. I was very pleased with this - although at this price it is the least you should expect.
Obviously, I can't judge long-term durability as yet, but I would hope that they will last at least as long as the Triple-fi 10s. I will edit my review at a later date should this prove not to be the case.