Last month, I moved my basketball coach off IE and onto Firefox. Yesterday, I made Brian's mom do the same thing. Despite my (heeded!) warnings to NOT click any popups, to only click the Windows close box in the upper corner, Ad Aware and Spybot S&D reported a raft of crap since my last visit.
As always, none of my Macintoshes have any problems. I'm moving from Netscape 7.2 to Firefox on those too, and am mostly happy. Where I'm not happy is that Firefox fails to import bookmarks from Netscape. It destroys them instead. And new tabs don't automatically open the home page.