I too am out at CES in Las Vegas, where it is now after midnight. (I work in the video side of the consumer electronics business.) Purely by chance, I happened to see a Sennheiser HD800 on static display this evening. The Sennheiser rep declined to let me listen to them before the trade show opens on Thursday. However, I can add a few comments.
These are clearly 21st century headphones. They look quite slick in person, and the build quality appears to be excellent.
The Sennheiser rep told me that the engineers specifically chose not to use metal for the frame because of undesirable reverberations. The Leona plastic they chose is supposedly much better in that regard.
I was briefly able to try the HD800 on my head (not hooked up to any source). I thought the headband comfort was fantastic, but I wasn’t too keen on the earpads. (Of course, other users might feel differently.)
The physical size of the ear space is noticeably larger than the HD580/600/650. If you felt suffocated wearing those, the HD800 should be welcome relief.
The HD800 was amazingly transparent to outside sound. That is, with no source hooked up, it sounded almost like I wasn’t wearing any headphones at all.
The cable appears to be higher quality than the old HD600 series cable, and is said to be silver-plated copper. The cable connectors are definitely non-standard. They use two small pins recessed within round metal surrounds, rather than protruding from plastic as in the old design. The connectors seem much sturdier than the old style, and it might be a while before third party cable makers duplicate them.
I don't expect street prices to get below full MSRP until the HD800 supply exceeds demand. If Sennheiser really is hand making them in Germany, that could be a long wait.
Needless to say, I can’t wait to hear the HD800 at the show.