I think people stopped using IE about the same time they stopped posting in this really, really, really old thread.
I've been using Firefox for years and mastered most of the shortcut keys. It's fast, portable, and supports add-ons. The only thing I hate about Firefox is the memory leak. Sometimes Firefox alone can take up half of the CPU and the memory would go past 2 gigs! Other than that, Firefox is a great browser.
Even though Internet Explorer has the highest market share percentage, Firefox is by far a lot faster and has more add-ons. I use Firefox because it's better for more experienced users who are more computer savvy. However, sometimes I need to use Internet Explorer to test programs that I compile.