The first big turn-off: it doesn't have a simple checkbox for "Classic View". Boy, do I hate the non-classic UI... Hopefully, it will be added.
Aside from that, a very positive experience so far. Faster than Vista in probably every respect - installing, booting up, shutting down, running apps.
I'm running 3 identical 200GB hard drives on a 780G mobo with 8GB RAM, 6000+ CPU: XP, Vista, Win7. All 64-bit. Switching boot disks is done in the BIOS.
Diogen.