I use both IE and Firefox because some sites work better on one than the other. Also some sites Firefox won't load the images, I've been told this is due to it blocking and information from 3rd parties and that i need to disable the programs that cause this but I have no idea how to find all the programs that deal with third parties. This problem doesn't happen with IE so I use IE if FF doesn't load a sites images.
Opera's too touchy for me and I don't like how it's laid out and how some pages look terrible on it.
IE crashes every other second when I try to use it.. :/
I use Maxthon and Safari sometimes when using a second browser is a must. I really like Safari actually but it tends to freeze up on me a lot.