I've tested vista all the way from RC1 up to the RTM, and it's pretty good as an OS.
The actual thing is pretty stable.
You have to have the specs for it though. Otherwise it'll lag you down.
My new laptop is going to have Vista Ultimate on it.
I like vista personally. It does well with video, on average.
There ARE some bugs still.
However, compared with when XP first came into being, I was able to solve vista problems 90% faster than when XP came out.
Why spend money for ultimate? Cause I'm an OCD person that is obsessed with making it so people can't get into my stuff. And if I'll ever settle for less than the top in software, the world will probably implode.