Vista has flaws a-plenty BY DESIGN; XP didn't and doesn't. You can't compare deliberate design flaws with a few bugs or driver issues. The latter would always be fixed; the former won't ever be fixed because MS have lost the plot with Vista.
XP doesn't have flaws? Hmm.. just OTOH:
GDI? DPI scaling? Drag a window and it will very likely cause a 100% CPU usage spike? Any window that needed translucency requiring a ton of hacks and loads of CPU time?
Security? No least privilege mind set during development nor any UI to expose it exists on XP.
16-bit sound stack? Not a problem unless you want to watch hi-fidelity movies as is now becoming the norm

Inability to properly support IPv6?
Pretty big flaws for the world's most popular OS, going forward, wouldn't you say?

Never seen anyone use that as a reason to upgrade. In fact Windows has been pretty much rock solid stable for going on a decade now. Can't believe people are still talking about stabilityPeople saying Vista is stable so we should upgrade
