Just to throw a wrench into things, I actually use Opera as my primary browser. I've been using it for years, and still prefer it. I do use Firefox at work because it's (finally!) being allowed on a pilot basis, until now we could only use IE. That was only made bearable by installing Maxthon.
Don't get me wrong, I love Firefox as an alternative to IE, but I haven't found a compelling reason to switch away from Opera.