Yup it's crack once you get past the tiny learning curve with the new start menu.
Faster than Windows 7
Microsoft Security Essentials antivirus built-in
Boots up in like 10 seconds
ISO Mounting support (no need for apps Daemon Tools)
There's probably more but I'm feeling it so far. I think if you don't get used to/like the new Start menu than stick with Windows 7 because it's not changing. I've come to like it though so I don't see myself going back.
I had the face when I first installed the Release Preview. The splash screen barely appeared before I'm at the damn initial setup screen. Shutting down is almost instant as well.
Whatever folks' beef with Windows 8, performance will not be one of them.