Just to get this straight - yes, they are quite strongly bass-weighted. But a lot of people like that, myself included. I listen mostly to metal/rock, but also a lot of trance/club, and they pack a very satisfying thud. That's exactly what I wanted, in fact I returned an £85 pair of other top-brand headphones because their sound was too 'balanced' and lacked the bass that I craved.
The mic makes the headphones a hundred times better still. I use it all the time with my iPhone 3GS. It and the headphones integrate perfectly with Spotify (I don't actually use iTunes) and all phone alert sounds. If you get a call, the music fades. After the call is ended it fades back in. One niggle I have is that now in winter, with gloved hands, it is a bit annoying to locate and press the central pause/play button. Another niggle is that the mic is at the height of the collar, so it ends up rubbing against the zipper on my jacket, which transmits loudly through the wire and into the headphones. But that's just my jacket I suppose..
The build quality is very good. I have been using them heavily since November and nothing is coming apart yet. I love the fact that the cord detaches at the earphone - I have damaged headphones in the past by crouching, letting the wire go around my knee, and then standing up - rrrrrippp! So this is a safety release of a kind.
Comfort-wise, I have worn these for 6+ hours straight. They are heavier and have a tighter grip than say the Sennheiser PX100s that I had before, so your ears feel a bit tender after 3-4 hours, but a small massage and they are fine, and you can keep listening. The ears get a tiny bit clammy but nothing to speak of really.
They provide a good seal from outside noise, but if you have the volume quite low, you'll still have an awareness of traffic, which I think is very important. But in the Tube you can crank them up and hear hardly any external noise. They really do not leak sound, which is fantastic as I can't bear other people looking at me and thinking 'what a moron', like I do...
I have quite a large head, and need them on maximum headband extension, so if you have a huge head, it's worth being aware of that and try them on first.
So overall, yes they are expensive, but if I have them for even 3 years it will be more than worth it. They are great fun to listen through, and if I ran a charity that helped all the poor imbeciles who still use the earphones bundled with their phone or mp3 player, I would definitely be recommending these.