If you arent using the Windows 7 beta, DO IT! I am very happy with it and running it on all of my laptop/desktop machines.
The only down to it is Media Center seems pretty broken to me. I have 300+ DVDs ripped (yes, all legit!) to my Windows Home Server and playing them through My Movies(great plugin!) works great in Vista Media Center, but locks up 7 Media Center often. Hopefully they will get it sorted soon, as I love the rest of the OS.
You can check out My Movies here. I need to do a post soon about my Media Center journey, as it has been a job and a half! Actually, probably needs to be a couple posts. Also, I guess I should do one on my current project, the CarPuter!