Just like any other web developer worth his salt, I use Firebug on an almost daily basis at work. I was excited to see the new features and performance improvements in version 1.2. After about a week of usage, however, I started uncovering some disturbing behavior. This version of Firebug seems to be very buggy. Here’s what I’ve seen to date:

• The debugger freezes. I set a breakpoint, the breakpoint is hit but I can’t do anything. The only option is to reload the page to get everything working again.
• Incorrect error locations are shown in the console. Sometimes the filename is completely wrong; sometimes the error occurred in a different tab.
• The XHR inspector sometimes returns “null” even though a response was actually received.
• Firebug seems to detach from the web page from time to time, so anything I enter in the console isn’t evaluated correctly.

Due to these and other errors, I recommend to the team that people stick with Firebug 1.0 for debugging. Unfortunately, 1.0 doesn’t work with FIrefox 3, so we’ve been systematically forced to upgrade so we can test on that browser. I still keep a computer with Firefox 2 and Firebug 1.0 installed in case I get into some hairy messes with Firefox 3 and Firebug 1.2.

I’m not sure how Firebug became so unstable, but I really hope these issues are addressed soon. I’d be willing to forego any new features to get the old ones working more reliably.