I'm going to blow everyone's minds and cause massive fanboy butthurt: There's no noticeable difference in speed, stability or functionality between Firefox, Chrome and Internet Explorer. It's all down to personal preference, and I use Firefox because of its interface and various Mozilla Labs add-ons (Weave, Ubiquity in particular). It's still a tad ugly, sure, but the next major release will turn the tables.
Also, not even Google likes Opera.
Also, not even Google likes Opera.