IE8 is a great browser! I've been using it since the beta and never had a problem. It still beats Firefox any day of the week in speed.
IE8 is nothing but a pain in the azz. Its just not compatible enough.
I've been using IE7 since it came out and love it. Very user friendly. I've tried Firefox but occasionally run into a problem and have to resort back to Explorer. So finally gave up on it. IE7 coupled with XP Service Pack 3 has been very reliable and I never use any sort of popup blockers or security software. I've never had a single virus or malware issue since SP3 came out.
Vista from my experience is just XP with a bunch of garbage added to make it look different, run slower, be less compatible, and be less user friendly. I'll probably be using XP pro and explorer until the microsoft gestapo come and peel it out of my boney fingers.