I just got the last r+ needed to get Growl support checked into Mozilla CVS trunk, which is a huge personal accomplishment if I do say so myself. That means it’ll be available in Firefox 3.0, and most likely the Alpha 4 build due out soon. Somehow, I managed to get it done on schedule it seems (I probably just jinxed it though). I’m about to submit the final patch after giving it a good look-over once more. It’s been about five months since I started working on this – and am I glad that it is almost done! I’ll have at least one follow-up bug to do once this lands (dealing with localization), but it works as it stands now!
For those interested in keeping track with the bug, cc yourself to Bug 362685.