I've owned the DT-770/80 for several years. I already owned the Grado SR-125, and I was looking for a closed headphone for more bass and sound isolation. I chose the DT-770 because it was within my budget and well-regarded in the pro-music (as opposed to audiophile) community.
I can confirm that they are very comfortable. Sound isolation doesn't compare to my pair of airline-style earmuffs, but it's better than the open-air Grados, and more appropriate at work.
I'm not a bass-head, and although the bass extension is substantial, I don't get the feeling that it's unrealistically bassy. I listen to a wide variety of genres, from classical to jazz to rock to whatever and I hear more bass variation just from decisions made by the recording engineer than from the DT-770 vs. other phones.
Connected to a PC or iPod it will produce recognizable sound, but I think it sounds far better amplified. I've used: (1) the headphone jack of a 80s vintage NAD preamp; (2) an Audio-GD DAC-19/C2 combo and (3) an Audio-GD NFS 11.32.
I didn't feel the NAD had enough ommph (which is why I spent the big bucks on the DAC-19/C2). With either of the Audio-Gd amps, there's a ton of detail that comes though, the instruments and vocalists separate cleanly in the soundstage, and I hear the backup singers as distinct voices distinctly placed. A great deal of beauty comes though these phones and it does a solid job with some of my most difficult source material.
The last few weeks I've been listening to them alternately with a pair of Sennheiser HD-650s that I borrowed from a co-worker. Even against something far above its class, the DT-770 doesn't get blown out of the arena: it's just a ... different take... on the music. There are some songs where I actually prefer the DT-770... songs recorded in such a way that the HD-650s sound like you're listening through a vat of warm honey.
I'm currently looking for another set of headphones, but I'm prepared to spend 2x to 3x the amount I spent on the DT-770. At $180 (bhphoto.com) they provide a lot of value. (If this isn't too off-topic for an appreciation thread, if I were buying again, I would also look at the DT-880).
