Firefox is still great due to Tab Candy (best feature ever). They FINALLY got with the times and removed the stupid useless title bar like opera and chrome. Unfortunately, it feels less stable and polished...
Not to mention, the CTRL+SPACE hotkey for tab candy disappeared, and the devs don't seem to even notice. Cuts down workflow having to click the little button every time.
Opera, IMO has been at the top lately. I like chrome for it's minimalistic approach, however, I do miss tab grouping when I switch to it.
Keep in mind, I routinely use all three browsers in my every day browsing. I have at least 10 tabs going in each, and it helps me differentiate between research, fun, and work having separate browsers for each thing. Too bad you can't just save sessions for browsers, it's annoying to have to load tabs you don't even intend to work with.