I switched over from Maxthon (Maxthon.com
) to Firefox for a full month after I was able to get firefox configured similar to Maxthon (which was a major pain in the butt I might add). During that month, I was slightly impressed with the speed at which it can display web pages. However, after looking at it side by side with Maxthon, FF used close to twice as much ram on my laptop as Maxthon with the same pages (& # of pages) open. It didn't matter if both browsers had just 1 page open, on my laptop (Inspiron 8200 with WinXP SP2) FF used twice as much ram in every case I explored.
After a month, I ditched it and went back to Maxthon. The feature set of Maxthon is amazing and once I started using those features, it was hard to get along with FF'* lack of features or poorly written plugins (or whatever you call them) that try to duplicate said features.
Ofcourse, this is just my experience and you have to use what you like. FF is not for everyone, but neither is IE or Maxthon.