I've been using Mozilla since 0.9.3 and pretty much exclusively since 0.9.5. (I forget which version of Mozilla started supporting secure web pages satisfactorily, maybe that was 0.9.5.)
Alas, I still need Windows for my favorite games. And the new computer came with damned Windows XP which has IE integrated so tightly into the guts of the system that it's hard to tell exactly when it's being used. (Hint to Microsoft: The damn fancy HTML Email isn't worth the hassle of the constant security flaws.)