For about a year, Firebug was horribly unstable for me. It seemed that each time they introduced a bunch of new features, the crashing, hanging, and erratic behavior (e.g. breaking at a line of source code far removed from the actual breakpoint) got worse. Happily, though, the last release before this current one reversed that trend. It didn't eliminate the problems but it did make them tolerable, which was a relief. I hope this one doesn't revive the previous tradition!<p>I think part of the problem is that FB wasn't designed to work with large (or even medium-sized) JS programs. We bundle all our JS into one HTTP request. It's a few thousand lines, which is big enough to cause FB noticeable trouble. A lot of the fancy features they've been adding are pretty useless to me; I wish they would simply make the console and the debugger rock solid. (And fix things like the horrible way they print arrays...)