I spent some time at the show with the HD700. Listening-wise, even using my own gear, I was less than thrilled, but it was very loud in and around the Sennheiser booth, even in their "high-end" listening booth. However, what really shocked me about the HD700 was how cheap the plastic looked and felt. I was shocked by the lack of quality feel in a $1000 headphone. Even the HD580 is a more pleasing tactile experience. Of course, some would argue that the low weight achieved by the cheap plastic build is more comfortable than many other heavier headphones. And while the HD700 might be extremely comfortable (I couldn't try it long enough to find out), it just doesn't look or feel like a $1000 item.
Furthermore, I really dislike how Sennheiser copied the general look of the HD800 when building the HD700, but took out the high-grade materials, and the ring-radiator driver. Like or lump the HD800, at least it represented Sennheiser using their muscle to leverage a new headphone technology. The HD700 on the other hand, might as well be an HD595 in drag.
I actually had a better listening experience with the Beyer T70, but that might just have been the combination of the closed headphones and lower noise levels near the Beyer booth. I didn't get any of the tizziness I've heard in the past with Beyer Tesla headphones, though.