Paul, can you comment how Firebug fits into this?

I mean there is A LOT of people who routinely use Firebug. Heck, I am actually designing sites with it. So from my perspective the best thing moving forward would've been for Mozilla to adopt Firebug as a standard DevTool. Frankly, it pains me to see two almost identical tools being developed in parallel, while it would clearly benefit everyone much more if it were a single, unified effort, with freed up dev resources spent on something else.