I'm kinda puzzled why everyone is having problems with Vista. I know I'm not exactly a newbie when it comes to computers, but I've never had any problems with Vista. I could imagine it would be worse if you're running on hardware with drivers not designed for Vista.
I like Vista. It's not vastly better than XP, but it is a step up. The Aero interface is pretty much useless, but purdy. Security is improved, not only the functional aspect, but I find it a lot easier to setup permissions.
Network functionality? I don't know what problems SysMan has had, but I have a Linux PC, an XP PC and my Vista laptop - all on the same network, and all without problems.
What most people seem to dislike is the security dialogs (allow etc), but that doesn't bother me, as it is just a simple click, and second of all, you only need it when a program needs permission to write to a restricted folder (i.e. when you install a program, change the registry etc.) It's like switching to the superuser on linux. Perhaps you could even log on as administrator like you do on XP, but then the security goes down the drain.
I have yet to experience any viruses or spyware on Vista (but I didn't have many problems with them on XP either).
I'd say give it a try with a neutral mindset - especially if it's free.