I'm surprised you picked XP as the falling point. I didn't enjoy the days of reinstalling 95/98/ME every 6 months to avoid driver weirdness and seemingly random failures. XP was built on the foundation of 2000, which tended to make it more robust vs. its predecessors.
I mean, part of it is that I really hated the Fisher Price look to it, but it was also the first time I ever felt like I had to "hack" things to make stuff work. I had to muck with registry keys. Oh, and it was the first time that I noticed that Windows repair tools do not work.
I suspect I might have hated 9x more but I was pretty young when they came out and I didn't really "get into" computers until XP, and I disliked it enough to dual-boot Linux as a twelve year old.
Vista on the other hand...