I think a good general rule of thumb for things like this is to ask yourself 'What does it do that I can't do now?'. If the answer is nothing, then it's probably not worth upgrading just for the sake of having the latest thing. If there is something it does, then ask yourself if it's worth the hassle of dealing with the potential problems.

For me right now there's no compelling advantage vista has over xp. As time goes by it'll build up advantages and they'll fix bugs and instabilities, and eventually it'll be more of a hassle to stay with xp than to just upgrade

So what does vista do that you can't do with xp?