I use Tab Mix Plus for some of the extra control it gives me over how tabs operate (I can't even remember what, specifically, since it's one of the very first things I install nowadays). I don't use tab groups - I use windows to organize subtasks, and virtual desktops to groups subtasks into larger tasks.
I'm generally philosophically against applications tabbing their entire window, but I think a browser is a good place to have them, if for nothing else for the sake of easier unwinding of the browsing stack.