This arrived today - a week after I ordered it when Amazon was predicting it might take two months. Out of the box - and into the back of my hi-fi amplifier - the impressions are generally very good.
It's certainly small - my kitchen scales showed only 34g - so it's probably a good thing it doesn't need to be touched much, since it's really too light to stay in position. I'm using all-RCA connections, so don't need the included RCA-to-3.5mm cable, but it is reassuringly chunky and may well make a useful replacement for a cheaper one elsewhere in the house.
Pairing with an iPhone 4S was as easy as pressing the button on top of the unit - nothing to set on the phone apart from ensuring Bluetooth was on - and I was ready to stream. A live stream of BBC Radio 3 using iPlayer Radio sounded exactly as I'd hoped - clear and coherent, with the slight loss of orchestral scale that even the best-quality compressed streams tend to show. (Nothing to do with the Logitech - I'd have noticed that with anything but an FM tuner.) I went to Pure Music for tracks by Abba and Black Sabbath and found myself happily tapping my toes (or banging my head) and easily able to follow bass or drum parts as I wanted to. For something so affordable and easy to use - and considering that I want it mainly to let me explore new (to me) music that I may then decide to buy on CD - I am very impressed.
The old-model Logitech Bluetooth adapter drew some criticism for its low output level, and that is still the case here. Playing a CD from my collection at the same time as the same track from Pure Music, switching inputs meant I had to move the volume knob from 9 o'clockish to nearly 11 to maintain the same level. I may even drag out the multimeter to see if this is due to the actual output voltage (I'd expect 2V at the RCA sockets) or to a lower level in the Pure source material, and update this with the results. It's not enough to be a serious drawback - even 11 o'clock is still well within my 'sensible' limit - but it would be inconvenient to switch sources and find the CD volume uncomfortably loud.
I wasn't intending this to be a true hi-fi solution - the way I'll use it it will always be limited by the quality of the stream - but I'm very pleasantly surprised by how musical it seems to be. Playing Pure Music files and the same thing on CD back-to-back I notice the CD gives more space to the presentation, and that in particular drums sound more 'drummy' than through the Logitech, but that may be due as much to the compression of the source material as to anything the Logitech is doing. I still think this is a bit of a bargain. Significantly, it's good enough to show the difference in quality between streaming sources. With the same complex orchestral recording (Brahms 1, Chicago SO, Solti, which I also have on an LP) the Pure Music stream (128k) felt squashed into quite a narrow soundstage and a little short of life. By contrast, the Qobuz stream (320k) was much more expansive and vibrant, especially in the great brass fanfares. For streamed music, in other words, the Logitech will not be the limiting factor in listening quality. For a £30 device, this is very impressive.
UPDATE - TWO DAYS ON I'm enjoying this thing very much. Not to show off but to show how well it works, I should tell you this thirty-quid converter is feeding three grand's worth of amp and speakers, with compressed source material too, and it's not disgraced. In fact, I'd have to play it back to back with original CDs (from a player of similar calibre) to be able to tell you where the combination falls short. I've been happily exploring the Pure Music library for forgotten favourites - like Judas Priest's 'Out in the Cold', which sounds absolutely HUGE. Bass, rhythmic drive, little details in the treble - they're all there. Yes, I would get a little more music from the CDs but I wanted this to let me try new things I might only listen to once and it's well up to that task.
Pairing - or rather, connection - isn't perfect; if I've been using the phone elsewhere or with another device, I sometimes have to reselect the Logitech in Settings before it will play, but I can do that without crossing the room to where the unit is plugged in. There's occasionally a glitch or skip in the music, but that's to do with the phone's streaming connection or an interruption from another app, but we can't really fault the Logitech for that. Close apps you're not using if you want to keep the phone quiet.
This is a remarkably serious little box and I'm very pleased with it.