Pros: no headphone hair, in-your-face sound
Cons: exposed wires, clamping force
Seriously, these things are built to last. When the apocalypse occurs in 2012, this Sennheiser would be left intact (maybe the wires would get destroyed). And for future generations of the human race (or whoever takes over the earth), they would be a relic of the old world.
I own two pairs, one for work and one for portable use, I treat the portable headphone with utmost care, like a baby, while the one for work gets tossed around and daily abuse, and yet both look the same. On a note of the clamping force, the frame needs to burn in, so that the force loosens and optimum comfort is achieved.
Sound. How does it sound? It's a bit colored, I think. Definitely not neutral, but I've gotten over the "neutral stage" where I cared about neutral headphones, I just want to enjoy my music with clarity. The bass mids and highs are fairly even in terms of balance, but not perfectly balanced. What's very noticeable is that it has punchy bass like a Grado, not deep rumbling bass. And absolutely no soundstage, which creates intimacy, or in my case, that in-your-face-sound that you get from Grado. I use these for speed metal, thrash metal, power metal, traditional metal, etc. Metal that's fast and guitar driven. They're like a closed back Grado, but not as bright.
I got it for free from work, as this is what they use for their stuff such as recording, calibration, etc. They previously used V6's, 440's and T50RP's, but they settled for the HD 25-1 II. There is a huge increase in price to the consumer, but I'd imagine when a company purchase these, the difference is not all that great. They are the basic edition, but I wish I owned a pair of the Adidas versions. :(