I listened to a pair of these. I know the impulse is to ridicule a product like this because audiophiles make the mistake of thinking their standards for the sound quality of a product are some kind of absolute, which is not true. They're just a taste, and different people have different tastes. Sony is making these cans because there is a demand for them.
The sound, as you might expect, hypes the lower frequencies. No surprises there. These headphones have been tuned for experiencing modern hip hop, dance/electronica and dance-pop music. The way these types of music are EQ'd and mastered is that they typically feature sparse arrangements, with high end detail floating over a punchy low end (drums and bass), a lot of (multiband) compression in the mid and high range, and a very much hollowed-out midrange. This is what these headphones are designed to reproduce, and they do an excellent job at it. The bass is huge and well-controlled, with minimal ringing. This gives the impression of very clean and very subjectively loud (if you want it) reproduction. Dynamic range, subjectively, is excellent. Detail retrieval is good, although you don't get the ultimate extension at the high end that you get on some of the better IEMs.
These are not the headphones for listening to classical music, or even classic rock. That will sound tubby and opaque with too much low end. If your source lets you EQ the sound, you can readily deal with much of this. But these are not monitors and they are not designed for flat reproduction.
Build quality is quite good. Finish is pretty good, could be somewhat better given the pricing. A lot of attention has gone into making these cans comfortable, and they are very easy on the ears. They are not the lightest on-ear headphones, but they are not particularly heavy.
I think the price represents reasonable value. They are clearly better than entry-level headphones in the $100-$200 range. I think they compete quite well with and indeed outperform -- if you use them on the kind of music they were intended for -- serious headphones costing more (e.g. Sennheiser, Beyerdynamic or Shure cans in the $300 to $500 range).
Agree that you shouldn't buy a product simply because of its connection to a celebrity. Neither should you reject one for that reason. These are good headphones that consumers of this type of music will find very enjoyable.
Only one post... Bigging up the Cowell Cans... mmm.. is that you Simon??
If so, Welcome to Head-fi and sorry for your wallet! (Although I think your wallet will be ok. Do you even have a wallet..?,Bet you have someone to carry it for you even if you do. Bet he even sorts out the 20p bit that you have to put in the lockers at the swimming baths...or when you fancy a Twix etc.. blaha blah)