I have always been a fan of Firefox and encouraged other developers to use it, addons such as Firebug and YSlow are simply essential tools for anything more than your most basic web page, and will even help with those. Neither the developer tools in Chrome, Safari or IE can really compete.
There certainly does seem to be an issue with the latest version of Firefox though regarding memory management, I am constantly seeing usage spiral up to around and over the 1GB value and become clunky and slow to respond. It looks like there is some effort going on at Mozilla to catch the culprits generally suspected to be certain addons, but personally I only used a few and still see the problem. I am looking at running some tests of my own to try and establish what is causing the issue. Firefox has been top of my toolbox for quite some time and it needs to stay that way.
Update:06-04-12 – Testing change to “Browser.sessionhistory.max”
Apparently Firefox defaults to storing 8 pages of history for each Tab that is open. This can be adjusted by setting “Browser.sessionhistory.max”
Default value is -1
Testing value set to 3.