I now have two main computers (both newish 'core' quads w/4GB RAM) networked via a hub, one has Vista Premium and the other has XP Pro. I have to say I haven't had any reason to complain about Vista other than two hardware driver availability issues...both resolved by Windows driver update. I think Vista is actually a smarter OS than XP by a good margin, it seems to learn how to make things run smoothly for you, wheras XP repeats the same mistakes time after time, example: I boot the XP machine and each time it's the same thing, it has to run network diagnostics to connect to the home network and internet, (initially it sees the network hub but not the broadband modem on the other side of it), the Vista machine is also connected to the same hub but never has any problem.
I have a yearly subsciption to Microsoft 'Live One Care' that covers 3 computers for about $100. With that I don't need any third party virus checkers or firewalls scruffing up the system, and it does a weekly auto backup to each external HD for each machine of the file types I have selected, and it also keeps the systems clean and mean via a complete monthly tune up.