Since OS X Lion, I've found Safari to be particularly frustrating (deadly slow and too many freezes), so I've switched to Chrome.
Firefox still does nothing for me, and Chrome supports the important plugins I use, namely 1Password and Evernote.
Chrome also wins over Firefox because Google, unlike Mozilla, could actually be bothered to enhance Chrome for Lion (mostly). There really is nothing worse/uglier than a Windows program ported straight to the Mac with no UI / UX consideration