Hi Genau
I've been using Vista since about September 07 and had no issues with it whatsoever - it's been stable, reliable, well performing. I had a couple of issues which I had sorted within 45 mins - but if anyone less PC techy than me came across the issue would cause them to tear their hair out !
Overall, I'd say you can go for Vista no worries at all. Service Pack 1 is now also out and improves the base code. It's not 'all there' though - there are always issues and upgrades etc but if your a basic to intermediate home user doing the 'usual' home based PC related stuff, you'll be fine.
Please also bear in mind any software you have or want - ensure you get and use Vista certified versions ONLY. Older programs will run in what's called 'compatibility mode' but I'd rather suggest getting an upgrade to an older program that's Vista certified - just to 'minimise' any risk of hair pulling out!
Late 2009, and Windows 7 is touted 'currently' for release - that aims to be the 'fix' that Vista was supposed to be.
In business and enterprise use, Vista desktop has yet to still take off in any major way but the similar 'Vista' ish code is being used to very warm praise in business level software.
If you 'really' must have XP - then as already suggested, using VMware and/or Virtual PC 2007 (this is microsofts freeby) - both free, you can 'run' XP 'inside' Vista in a virtual environment - and works stably and very well indeed. You only have to make sure you have a genuine licensed copy of XP to do this though.
8/10 for me by using Vista !
Cheers, DtM! West London & Slough UK!