mmmmmmm Firefox has some problems in some sites, for example in myspace some spaces doens't appear like the original, and something like that, but Firefox still the Best.
basicly firefox & IE have different read method, but if you want use firefox fully you can install add on that aviable on mozilla official site.
now i use firefox because have better securities for my money maker campaign, but i am too use other IE based browser like flock if i have difficult with a site.
my suggest is use 2 browser is no problem & maybe will make you beeter surfing.
Yeah I use mostly firefox but my mom and sis rather using IE so I have them both installed here so if it doesnt open on firefox I go check IE... there are a few cases that the page doesnt work in both... but then I think its the webmaster problem =/