BUT...twice Windows update changed my manufacturers(pre-installed) WI-FI driver to a GENERIC Windows one and I lost Internet connection!!!
Never had this happen, but the easy fix would have been to set the updates not to install anything unless you said to. I usually only recommend automatic updates for people that are pretty computer-clueless. You'd just get a pop-up notice every once in awhile (once a week or so) that says you have updates waiting. Take a look, pick the ones you want, remove the others.
WinXP was pretty good, but constantly under assault. Win7 has been bullet-proof in comparison. That alone is reason to upgrade (not to mention that XP feels positively primitive after using Win7 for a few months.)
IMO, the problems with Vista were greatly exaggerated and I find that most people who claim to hate it never spent any real time on it. I only ever spent any real time with it on one computer (my Mother's) as I went from XP to 7 on my rigs, but she never had any issues and I generally do maintenance on her computer about twice a year since she's not very computer literate. In fact, she's still running Vista without problem.
Win 7 (32 and 64) have been fantastic and I've been using it since pre-release. There really isn't anything I don't like about it and have been running it on all my computers (HTPC, Production, Game, Laptops, etc.) All issues I've ever had with Win 7 have been graphic driver related and falling back to earlier versions of moving up to a beta has usually fixed things.
I'll be jumping on a Win 8 tablet when it releases and will put it on my HTPC to test the waters. Unbiased reviews have been solid, but like jfrazierjr mentioned, there could be some driver issues on initial release (usually on older or poorly supported hardware.)
BTW, anyone who wants to check out the Win8 Developer Preview can: http://msdn.microsoft.com/en-us/windows/apps/br229516