The bottom line: If you buy a new PC, you pretty much don't have a choice (unless you buy a Mac). But for upgrading, better wait for SP1 and video driver updates.
Other points:
- Vista needs at least 1GB of RAM to function smoothly, but 2-4 if you want to run more than one application at the same time.
- Vista uses memory better than XP, so 3-4 GB actually makes a difference.
- Vista's file system caches applications you use most in memory, so they launch faster.
- A new video driver architecture was created, which means all the graphic card companies are basically starting from scratch. Performance and compatibility are average, but will get better.
- The Aero interface is pretty but not practical. Contrast that with Mac OS, which merges both beautifully.
- The default user account isn't a full Administrator level, and there are more security safeguards. However you can simply disable all that and be just as unsecure as XP.
- The included apps like Windows Mail, Calendar, etc. are just as lame as they've always been.
