Ahhh full detailed review? My ears aren't discerning enough!
Here are some first impressions. I've been listening for about 2 hours or so, so everything is subject to change.
They really are super comfortable. Noise isolation is pretty respectable. They get the job done for the office. The big reason I went with these headphones is to cut down on office noise (mainly HVAC and random chattering) so I could listen to music without having to pump it up to loud volumes, and they do just that. They attenuate the HVAC noise, though not completely. Some low-frequency fan noise still comes through (that will affect some impressions on sound quality I've had). I can also still hear people talking, which isn't a bad thing, as I need to know if someone's calling for me.
Still, having headphones that can provide a solid 10 dB of noise reduction while not clamping down on one's head is really amazing. They might be a tad sweaty in a warm environment, but that should not be a problem in the office. I think the HD-580's are more comfy because they're not as sweaty, but they're not that much more comfy.
I'm listening to it straight out of the box (no break-in), straight out of my ipod, and with no amp (which I don't have yet). It does sound quite good. They do sound airy like open headphones.
Bass certainly has some punch it. More than my Sennheiser HD-580's and maybe more than my Grado HF-1's (same as SR-225). It's not exactly slapping on a subwoofer to my head, but there are some moments where I can feel the bass a little. The HVAC noise that still gets through the headphones tends to be low-frequency, so it's possible some of the bass gets lost in the noise. Bass lines still aren't as clear as my speaker/subwoofer system, but that could be due to the noise. Still, they are more prominent than on my HD-580's without being overwhelming.
I heard before getting it that the mids were a bit recessed relative to the bass and treble, but I haven't noticed it too much. They feel pretty smooth. Treble isn't as bright as the HF-1's (SR-225's), but that's understandable because the Grados are pretty bright. Treble is detailed and clear without being harsh. Stuff like Miles Davis' trumpet on some recordings (or Bob Dylan's harmonica) can be pretty harsh on my Grados, but I think they're more tolerable on my D2000's.
So, The D2000's more upfront than the Sennheiser HD-580's which are pretty laidback, but they're kind of airy like the Senns and are also pretty smooth. They're maybe not as upfront as Grados, but not as harsh either. Bass is quite solid without being overwhelming. And it's all in a closed, reasonably sound-isolating, super comfy package. They're really great and perfect for an office environment and sound quite good unamped.