I bought a pair off Amazon when the were selling for around $175. Really nice headphones, but the sounded a bit thin and tended to over emphasize the highs.
I bought a pair of HD600s for comparison's sake and have some HD650s due to arrive tomorrow. In the meantime, I can only offer that I still like the Beyers. Compared to the Senns, they have a wider soundstage and (to my ears at least) a slightly more natural sound.
Interested in your impressions, though.