One thing we hear a lot from Firebug users is that Firebug slows down Firefox. When Firebug is active, particularly when you’ve enabled the Console/Script panels, some pages perform much more slowly. Enabling these panels turns on all of our debugging hooks, so some slowdown isn’t surprising, but what may surprise you is that, in order to get accurate debugging information, these hooks also turn off Firefox’ high-performance Javascript JIT compiler, even when Firebug is inactive. And now we have a fix for that.