I am running Windows Vista on my high-end desktop machine, but even then, it is rather slow. It is purty though, I'll have to give you that.
The truth is, Vista is great if you have a machine that can handle it. Most of us don't have that advantage. I know my new laptop is coming with Vista, but it's also been boosted to its highest level of processor and ram, so that it can run it. I'd no more install Vista on my older laptops or desktops than I would try to install a MAC OS on them. It just isn't going to work on older machines.
That being said, I work on a large college campus, and we are not moving to Vista anytime soon, either. We have it deployed in one classroom where we are teaching it, but that is about it. There are no immediate plans to deploy it, either, because our equipment just will not run it, and the higher costs of newer machines is not in our budget during an economic crisis.