I would never go back to XP.
Further more, My friend games on a middle-end dell inspiron and he can play COD on lower settings just fine, and WoW runs great.
Vista is designed to be run on current hardware, someone that just installs it on their 5 year old computer and complains it runs slow isn't really doing any justice to it. Its like running XP on a computer that was designed for Windows 95, it will run it, but really badly.
I have a Duel Core laptop with a GeForce 8 and 2gb of ram running Vista Home Premium, I love to use it. I also have a desktop computer with Duel Core 6200+ and a GeForce 9800GTX+ running Vista Business, its amazing, infact it runs vista faster than it can run XP.
People act like XP was like getting sucked off by an angel from day one. It was the same thing. Everyone hated XP because it was apparently a total resource hog, and had too many features, and bla bla bla.
Time to move forward people. You can buy a sub-$900 computer with 6GB - 6,000 megabytes - of system memory. A $499 system will get you 2-4GB depending on sales. Fucking upgrade your old ass hardware, or if your new hardware is slow, you've likely got spyware/virus/fragmentation/temp files holding you down.
As far as system speed goes, when I first tried running Half Life 2 on my computer under Vista, it was almost unbearably slow even on the lowest settings. It averaged about 8-10fps. On XP, it was delightfully quick, running at about 30fps on average. Just a few days ago, I tried it again on Vista, and I was averaging about 25-30fps, so there was little to no difference in system speed at that point.
However, it is true that older hardware will not adapt well to Vista; anything less than 2gb of RAM will be sluggish at best.
Vista had some problems in the first month or two of its release, and most of those problems were actually 3rd party drivers (nVidia, ATI, creative, etc). Not microsoft's responsibility.
Most people who dog on Vista are too stupid to know why they hate it, and its usually because they dont hae a computer that meets the requirements to run it.
I'm pretty sure though, that a lot of people say Vista is crap just to fill a bandwagon.
I downgraded. Vista sux.
QFT