Vista on my Laptop takes 4 mins to boot, on the same system i can boot debian sid and run a virtual machine with xp Yup, vista uses considerably more ram, this slows everything down, i know people say vista is more secure, but honestly if people knew how to secure xp in the first place there would be no need for vista But after boot debian takes 300MB / 2GB of ram and i have to run azureus and a vm with xp to get closer to 2GB of usage, after a few weeks of uptime it shows that stuff like xgl, kde, and compiz fusion still take up a total of about 300MB of ram and most of the rest of ram is used as a disk cache for ultra fast loading of the apps that have already been restarted, thats what i really love, how you can start a slow app, close it, and when you restart it next time it starts amazingly fast
I run vista now on my PC, and most stuff works with it - there are some problems yes, but it's new - every version of Windows seems to have problems in the first year or so. I wouldn't encourange anyone who already owned XP to shell out for an upgrade, but I wouldn't avoid buying a new PC just because it had vista on it either.
There's been talks that businesses in general are going to skip Vista & go with whatever Microsoft is releasing in 2009-2010, Windows 7 I believe it's called.