I use and love Opera. Speed Dial, Notes, Mouse Gestures... I don't know how I ever lived without them. XD I also like how it saves all my tabs when I exit, so I can pick up from where I left off when I come back. :D
I've tried Firefox, and things about it just bother me. My main little annoyance is the way that you click the scroll wheel, and if you have to click it again to get off of it, while Opera and other browsers just let you continue scrolling. It makes me want to kill someone. Also, opening a blank tab is kind of a pain. >___>
I sometimes use Flock, but for normal browsing I stick with Opera.