It seems like a lot of people are learning this lesson with Vista these days. There are very few applications that require Vista, and XP works fine for most people, so why upgrade? There's really no harm in waiting, while the ISV's, hardware vendors, and MS sort it all out.
Personally, I'm terrible at this. Anything that's shiny and new I have to try, usually based on false hope that things will be better. I'm usually disappointed that things are the same†. As a technologist, it seems that one needs to keep up on the new stuff, and the best way of doing that is by trying to adopt things as they come out. But often, the time I waste dealing with problems of the new stuff offsets any potential benefit. I realize more and more that the true skill of a technologist is to be able to see which of the new things are really worth adopting, and spending time to master those things.
One person I know is extremely good at sticking with what works: my dad. He's just now moving to XP. He uses Win2000 on his main machine, and has a little prototype XP box that he's gradually moving over to. I guess he'll have a great many more happy computing years coming up, and maybe he will never even know how bad Vista really was.
† that's not to say there aren't notable exceptions. I'm pretty impressed with Gimp 2.4 so far. And Lightroom has really changed how I look at photo management. But again, these are rare occurences.