There are already couple of discussions/reviews about the new and improved Mozilla Firefox 3 memory management but i was amazed from the amount of work they have done.
Worth reading is the original blog post from Pavlov explaining the methods he and the other developers used for optimizing Firefox 3 memory usage, caching and fighting against leaks. The post is a bit long but there is very intersting information that is quite usable for almost every application developer.
Also couple of days ago Arstechnica compared IE7, Firefox 2, Opera 9.5 Beta, Safari 3.0.4 Beta and Firefox 3 beta 4 and proved that there is obvious improvement and FF 3 uses less memory than other browsers.
With the new look and redone bookmarking system (sqllite as backend and location autocomplete from the bookmarks) I will still stick with Firefox as preferred browser.
Couple of screenshots:
And because for some IE8 vs Firefox is not interesting enough I suggest checking the newly released Safari 3.1