I've been using Firefox back when it was still Firebird. Being one of the few who isn't impressed with Firefox 3, I might switch to Chrome or go back to Opera though.
Ever try using a browser compatibility checker? Other than few odd cases, IE8, FF, Chrome and Opera should all render a website the same way. IE7 of course renders sites "Microsoftly".
I use chrome at work and firefox at home (chrome doesn't work for macs yet, wtf!). I love chrome... its the coolest. But firefox has stumbleupon which may be the greatest invention since the fish tank.
I've had bad experiences with IE and never really liked the browser format. I have tried Chrome but I'm probably going to wait until everything is done to start using it.