I think the main advantage xp has is in the developers sense, there are years of work put into everything that's on xp but relatively little for vista. Many patches and programs are still waiting for proper Vista releases (if you have to use Omega Drivers to play your favorite game then you know exactly what i'm talking about). Omega vista drivers aren't even ready, and even then they will be the first release, while the xp Omega on the other hand is very solid and well tweaked.
So it only makes sense that ppl assume Vista is to blame for these problems. Especially if you are talking about indie developers who don't have a team of 50 ppl to work overtime the day vista came out to have a compatable version.
I used vista for two months and overall, i agree with what you said....once i had enough ram, and removed lots of the useless features (like that stupid protection scheme that makes you say yes or no to EVERYTHING) it runs comparable to xp on this pc.
But my GE doesn't export right in Vista, and it does export right in xp. It might not be vista, but maybe a driver difference other (my xp soundcard doesn't work in vista and vice versa). Point is it works in XP!