The problem with Vista is it hogs all your resources, and adds absolutley nothing. Windows Aero? what does it actaully DO? Now, if we could move from one screen to the next and switch focus, that would do something, but we can't. Seriosuly, name me on useful feature NOT called DX.10!
As for the 4GB Limit on 32bit systems: If vista didn't need 1GB to run, and 2GB to run well, there wouldn't be an issue with lack of RAM. You get diminishing returns after 2.5GB system RAM anyway, so unless you CF/SLI two 768+MB GFX cards, you shouldn't have any memory issues whatsoever under a 32bit OS.
To prove my point: I have two games I run on Vista, CoH and Crysis. When I run both in DX 9 mode, the XP install is always about 5 FPS faster, even though XP can only see ~2.75GB of my 6GB RAM. Why? Because Vista is slow and unoptimized.
I also find it funny, people complain about how unstable XP was when it came out (still as stable as 98SE though), but Vista was just as bad (I had a "File System Error" while installing to a pre-formated disk).
Finally, the reason coorporations won't use vista is simple: They recylce computers (my work comp is a Pentium III 1.2 GHz). We can't RUN vista, so why upgrade when XP works?
Also note: You can NOT run 16bit apps under Vista, as they are no longer supported. I need an OS that supports 16bits, because thats what all the software I need for work is written in.