So, I guess I'm in an interesting position. I have two pairs of D2000s here; one that has a couple hundred hours of run time on them and a brand new pair that I got today from J&R.
Well, using all the same gear they sound different. They're subtle differences, but they're there. With the newer pair, mine, the bass is a little muddy, the highs are a tad too sharp, and there's an overall sense of "artificialness" to their sound. The older pair are more D7000-like; tighter bass, smooth clear highs, and have a more organic quality. Well, personally, this seems to put to bed the questions regarding headphone break-in, at least for dynamics. I'm going to hold on to my friend's set for a couple days for comparison, but I feel rather confident that they'll both sound much more alike after mine have simmered for a day or two. I like this, it's been educational.