I'm not sure what hardware you guys have tried vista on to say its slow but I find it pretty much as responsive as XP. I use Vista Business 32bit at work on a Core2 Duo E6300 system with 2gig ram and at home I run Vista Ultimate 64bit on a Core2 Duo E6600 with 4gig ram.
I've also installed Vista business from our MSDN version on a P3 800Mhz with 768mb ram, 40gig HD and a Radeon 8500. Was very usable to be honest.
Also I have encountered only two devices so far I was unable to get working. One was my old (and I mean old) Audiophile 2496 sound card which I dont even use anymore and a Logitech webcam. Also these problems were on the 64bit version. The webcam does work in the 32bit version.
As for it being resource intensive - it really isnt. If you have the ram, it will take all of it using its superfetch service which preloads some items instead of leaving the ram unused. This speeds of launching of commonly used apps. If you dont want this feature, it can be turned off via services. It uses much more disk space than XP - about 12gig on a clean install but its because it installed all options on the HD. There is no more add/remove windows components. There is only turning on/off now. This is not an issue anymore as the smallest HD you can possibly buy is 74gig these days unless you go out of the way to get a smaller one.
The security nagging thing is just a way for everyone to bit*h. You can disable it with like 2 clicks and the computer will be have like XP. I'd leave it enabled if I gave a computer to my mother.... lets put it that way.
Game performance is slower as drivers are not as mature. Its a huge problem. I benchmark 171 FPS in Doom3 instead of 190 FPS. I dont even know how I can live with this performance hit.
Too many versions? Hows that a problem. Just frigging pick one. I mean how the hell can you shop at a grocery store with SOOOOO many things on the shelf if you cant decide on a version of Vista. Decide what you cannot live without and pick the right version that will fit the bill.
Vista has been as rock solid as XP for me on both systems so I'm unaware of the instability problems. Also my GF is not calling me all the time with help with vista on her notebook so obviously she's doing fine too. Incidentally she purchased the cheapes POS Toshiba she could get which has 512mb RAM, shared memory and Vista Basic. Oh and a Celeron CPU too. Vista is still not horribly bad on there. Yes its slow but much better than I would have imagined it to be.
Anyway thats all. People whined the same when XP first came out too so......