I switched to Firefox awhile back and despite genuinely liking IE, don't miss it. I'm using a laptop with IE on it right now though and realizing how awful some of the bugs are.
When downloading a large file (500 megs), it downloads it to some random spot in a cache somewhere and then when it's done, copies the file to its actual destination. On this screwed up laptop the copy is taking longer than the download. Why copy at all?
When the on-disk cache gets too big it bugs out in weird ways. The most notable symptom is intra-page links (via #foo in the href) fail. You click them, you go to the top of the page, not the anchor. Doesn't this bother anyone else?
A similar bug; if you have too many URLs in your browser history IE stops colouring the ones you've visited differently. Only fix is to flush the browser history.
Most of these bugs have been in IE for at least three years. Where the hell is the fix? Oh yeah, Microsoft achieved a monopoly in browser share and abandoned development for two years. Good thing someone came up with a real alternative.