For a product that's so compact this headset gives very good sound quality. For those music purists this won't be good enough but what are you expecting for a mobile phone headset?!
I use this for when I'm out cycling and have attached it to the underside of the peak on my cycle helmet with the wires neatly cable tied to the inside of the helmet. I find that this gives me a very versatile means of listening to music whilst cycling without getting tied up by cables. The only downside is not being able to access the volume control on the device but this a small price to pay for convenience.
As for compatability, i've used this on 2 different Sony Ericsson phones now, an Experia X10 min pro and an Experia Ray and it works seemlessly with both giving good sound quality and easy installation and use.
Turn it on, turn on Bluetooth on my phone, press play and off I go.
There is the occasional dead spot, which I assume is down to a loss of bluetooth connection but this never lasts for more than 1 second. A great product overall and I would definitely recommend this to a friend.