UPDATE - july 2nd
Since my post yesterday, the firebug developers have released another version of the tool (1.4.0b4) it seems more stable, great job!
When Mozilla launched Firefox 3.5 a couple days ago, I was forced to upgrade my FB (firebug) to the new 1.4 beta version, although the new FB has been greatly improved it still has a lot bugs as you’d expect on a beta version, but that’s not the bad part, the new FF3.5 is really fast and has really cool new features but FB is making the browser choke and freeze all the time, it’s no news that FB has become more and more slow and buggy each version.
I don’t mean to sound harsh and I have always been a fan of FB, it was the one tool that brought us from the dark ages of alert() debugging to a more professional debugging, but something has to be done urgently, rightnow you can’t even think about debugging heavy web apps.
So, what could be done? Maybe Mozilla could adopt it as part of the browser, I know it would probably need major refactoring, but as far as I can tell built-in tools are much faster, like Webkit’s Web Inspector (Safari only, the Chrome implementation has a lot of bug fixing to do) and also Opera’s Dragonfly, as for IE… well you know, not worth mentioning ;) Or maybe the FB developers could focus more on performance than adding new features.
I know I could switch to Safari, Chrome or even Opera, but the point is FF really deserves a great developer tool like FB was a while ago :)