I recently got these to replace my ageing iPod touch 'phones, and the increase in quality is immediately clear. As I'm a music student, I needed high quality and good noise reduction for listening to classical music on the move; thus, I thought this in-ear solution from Sony would be the best choice for my 20 quid price limit (I repeat: I'm a student!).
Well, for the cash, these headphones are very good. The noise reduction is incredible - these things are more effective than most earplugs I've tried! You can walk down a busy road and be totally unaware of passing traffic. I must say, however, that since buying these ear-phones I've had several close calls with said traffic whilst crossing the road because of this!
The sound quality is okay. It's very reasonable for the price-tag, but in the scheme of things is quite low on the scale. The very highest-pitched sounds - cymbal crashes, especially - are tinny and lack any depth whatsoever. The bass is fantastic - as one would expect from "X-Bass" earphones - but is sometimes slightly overpowering, so much that I had to adjust my iPod's equaliser to accommodate. However, they're versatile 'phones and I've found that they produce an acceptable sound playing all of my music: Classical, Jazz, Rock, Electronic, and Metal.
As for comfort... could be better. The three different-sized ear buds provided with these 'phones will accommodate almost all ears, though even with the best fitting ones you'll sometimes find that movement causes them to slip out. You wouldn't want to by these for jogging, certainly. Also, because the ear-buds fit so snugly inside the ears, it is possible to hear the rubbing of the wire/bud with every step - this is a small gripe but is sometimes distracting when listening to music on the move.
In all, a very good buy. I'd recommend these phones to somebody on a tight budget: in this price bracket, you simply won't find anything better. However, if you've got a bit of cash to spend and you're somebody who really values professional-quality sound; or you intend to use these 'phones whilst doing something active (ie. jogging, gym, etc.), I'd look elsewhere.