Perfect for use away from home if you want music that's not too far removed from a home system! The sound quality blew my mind. Try these with the W810i for the best quality sound - surprisingly they don't use up too much battery power either (but they do with the k750i - ouch!).
Only drawback I've found is they don't fit perfectly in my k750i so well and I had to play around with the connection a bit (the end result was worthit), but as I now have the w810i, it's no big deal. Well worth the money for all Sony Ericsson owners.