Most people that use IE do so because they don't know there are better browsers.
Often when I ask someone "Which browser do you use?", I get "What's a browser?"
People that use Firefox use it because they think it is an OS, they regard extentions
as programs they download.

I will probably upgrade to IE 9 when it comes out of
beta. I will do so for the security updates.
IE's security weaknesses weaken Windows OS's.
I sometimes use IE 8 on 7 64bit as I'm testing the Adobe Square Flash Player Beta for 64bit IE.
The only other time I use IE is for logmein.