Opera is the best browser on the market. You should give it a try. Pretty much every good feature in Firefox they copied from Opera in one way or another. It's also not a memory hog like FF.
EDIT:
here's a list of some popular Firefox addons and their Opera equivalent. Opera has a lot of their functionality built in by default.
thibi - Firefox Extensions to Opera UserJS and Extensions
Good to know, I might give Opera a try. I've been using Firefox with Firemin (3rd party program that stops Firefox from eating all your memory).