Wow, after reading this thread, I was expecting something very different than what I found when I tried the 2006 DT880 last weekend. In just about every way, I found I preferred the K701 to the DT880 (clarity, detail, speed, balance, depth, soundstage, imaging, instrument separation) with a more a natural and involving sound as well. The DT880's sound was more like listening to a sort of small-speakers-on-my-head sort of presentation compared to the 701, and I really didn't feel it was in the same class as a headphone. It still sounded very good on its own, but I found the K701 eclipsed in a significant fashion. I also couldn't get over this feeling with the DT880 where, when listening to music, it sounded like I was in a noisy room. I'm not sure what it was picking up, but it did this on all the amps and sources I tried as well as source material, so I guess it was just something about its presentation.
The DT880 still remains in my top 10, but the K701 has probably managed to boot it out of the top 5 while making space for others in that section.
I must thank kitaoji (an awesome head-fier with impressive headphone analysation skills
) for helping me out so much in letting me hear both her DT880s and her K701s. My K701s are defective, so it was good to hear the real-deal, as it were, with the 701s versus the 880s. There was another pair of 701s there, as well, with 500+ hours of use. I'm definitely going to stick with the 701, although I could see having the 880s for those few occasions where I leaned towards the 880s a bit. Although, the GS-1000 did a better job for those occasions, so maybe I just have to save save save
This is first impressions, though, so maybe on repeated testing I'd find somewhat differently, though I doubt the general impression will change much. One thing I absolutely feel I must say is the DT880 comes in far superior packaging, IMHO, to the K701. I love that Beyer case + foam and wish AKG had ponied up for it as well as it's definitely an asset and the 701's package is almost disgraceful by comparison :P.