Oh yeah, Firefox is also more secure and lets you block ads and malicious scripts automatically. And there is a syndicated list of all known ads, whether they be page elements, images, or Flash, so that ads stay blocked. Microsoft would never want to do something like that.
In all honesty, Internet Explorer feels rather clunky after using Firefox. IE is unexpandable, doesn't handle new windows as tabs, has security holes, has an inaccurate and slow rendering engine, and has next to no community involvement. More and more web developers are deciding to add support to Firefox, and if a site still doesn't work under said browser, you can always use IETab to switch rendering engines.
Seriously, in all the time I've used Firefox, the only spyware I've ever gotten came in the form of harmless cookies. I can't recall the last time I got any other kind of spyware, or any virus that wasn't a false positive, from using Firefox. Under this light, there's really no reason to go back to Internet Explorer.
And if you hate Firefox so much for its memory leak that already has a fix, you could always try Opera. There's a browser that has a good wealth of features and is secure as well, and it looks to have some pretty strong community involvement. It's not quite as versatile as Firefox in my opinion, but it definitely has its fans.