I like Firefox.
Yea so it uses a bit more memory, I also have 2gb of RAM and have never gone passed the 1gb mark so..and if I have it might be just barely over.
That and I like all the addons even if I only use a few that I dem necessary. Its the choice and the fact that their there.
As far as addons I have 8 installed, one is a dictionary for spellcheck.
edit:
Although one thing I like about Opera that Firefox doesn't have is you can right click in a searchbar and make a search engine for Opera right there on the spot.
Then again I hate how Opera manages RSS feeds.