Sweet.  I didn’t see this before, but Firebug has a new beta version too, which means that it works in Firefox 3 beta 4.  Grab it from the releases page under the Firebug 1.1 Betas heading.  Possibly the single most useful Firefox plugin for me, the fact that it wasn’t working in the beta releases of FF3 was what was stopping me from switching to the beta. No more excuses now, the Adblock Plus plugin even works.