I use Firefox... in fact I'm still using the beta version. I have a lot of extensions for it loaded that make tabbed browsing even more efficient. And I like the way you can search for text on a page just by typing... you don't have to choose a "find" menu command or anything. I think they changed that in the released version though. Poo.

I keep IE available so that I can check the web pages I create in it, and also for pages that have problems in Firefox. I don't seem to ever really have display issues, but sometimes forms won't fill out properly (again, forms created with programming that is adjusted to the IE way of doing things) so I use IE for that.