I can definitely tell you to steer clear of any of the lower end vista installs, because you'll lose:
- Ability to do simple backups to a disc not physically connected to your machine;
- Term serv access to your machine from any other;
- Like Fry says, you'll lose RAM. I have 4, vista only "sees" 3.
I'm talking out of the box at least. I want to go x64 but really dreading having to reinstall everything.