I use IE, but I thought I'd try out Firefox to see what the fuss was about. I still haven't found out.
I found it slower than IE, I never used tabbed browsing and using my scroll wheel caused it to "jump" down the page rather than smoothly scrolling (a minor point, I know, but it's what I'm used to). Feature-wise, it was very similar to IE, with the exception of "revolutionary" tabbed browsing which I never used.
I don't know where you guys get spyware and browser hijacks from, as I've only ever got tracking cookies. I've also never had a virus. It all depends on what kind of sites you visit, hence IE is secure for my usage.