Sound and frequency response across the board is fantastic. Even with the pre-installed pads, the bass sounds clean and clear.
Build quality is top-notch
Comfortable, considering the size
Clamp force is a little tight, but that'll probably get better with time.
The ends of my ears touch the driver wall.
The noise of the spring pad as it settles into position is annoying, but as with the clamping, I suspect this will ease with time.
The cable. It's good quality, but the braiding keeps it somewhat tangled and I also will never use the microphone integrated into it. Instead of a 2nd pair of pads, I'd have preferred a 2nd cable [or maybe even a somewhat better cable]. Alongside this, I also prefer cables that connect via 1 side, instead of connecting directly to both. This makes them ambidextrous for sure, but I sometimes hit the cable during use.
I initially wanted the HE35x's or the HE4xx's [they were going to take at lesat a couple months before being shipped and I needed a new pair asap], so that's what I was initially going for, but I'm still happy with these. I've had M50x's with velour pads, and Status CB-1's, where the pads started falling apart. The sound quality is the same or better than the CB-1's; which is interesting considering they're the best quality budget closed cans you can get on the market [except for maybe Monoprice Retro's - which are difficult to get over here].
If you're looking for a good set of closed-back headphones, that have excellent build quality and a removable cable, then look no further, although seriously consider options in a lower price-bracket [like the Retro's + pad change]
One last thing: I initially used them with a regular 3.5 - 6.5mm adaptor, but of course there's a 4th pole in the cable that I'd forgotten about and the sound was very odd. I'd heard things in songs I'd never heard of before, but it basically made the mids very hollow and bass next to non-existent.
MAKE SURE TO USE THE BUNDLED 6.5mm ADAPTOR.