No, I want to spend my days using a browser that doesn't get in my way and let's me customize it to the way I work.
I do, however, use Firefox to check pages while I develop them, and then after the initial coding I'll double-check them in Opera and IE (and Mac versions as well). Firefox's Web Developer tools are very useful and don't really have an equivalent in Opera.
But for everyday browsing? Opera wins hands down.