Pros: The sound, comfortable, detachable cable, everything is replaceable, nice design, awesome price, forgiving with lower quality sources, low impedance
Cons: Hanger not included, not even a pouch, the 6.35 jack can be a problem
These are just insane. It has such a flat response, but they are not by any means boring. Every single frequency shines since the instrument separation is great. There is simply no distortion, even at really high volumes, which they can achieve very easily since they have a meager 50 Ohm impedance and very high sensitivity. If that wasn't enough, their best quality IMHO is their HUGE soundstage. Even while being so open, the bass in punchy and unlikely tight!
Everything is serviceable too, from the cable to the headband padding. The ear pads are big, cushy and don't get your ears too hot thanks to the open design of the cups themselves and the velour-type material. They are so soft you can almost forget you're wearing them. The headband is heavily padded with memory foam covered in white leatherette, as well as the headband itself. On that note, I think the design is great. Sober colors make it stand out of any other Sennheiser model out there.
They are forgiving with lower quality sources, although they tend to show off excessively EQ'd signals. Bass can be boosted but only to a certain degree, but I love the bass the way it is out of the box. After burn-in they become even more lush but retain the tight bass.
The ony issue is that cable that ends in a 6.35 mm headphone jack. Sennheiser includes an adaptor which adds a lot of bulk to the connector. I just use an adaptor and then a neutral extension so it doesn't stick out when using them with mobile sources, although their place is at home. I seriously can't recommend these enough.