To be quite frank, this is really ridiculous to me. Why in heck are there TWO separate developer tools for one browser that are both in-house? Supporting both tools means that neither one moves as quickly, and there's a ridiculous amount of confusion as to which one to use.
Imagine the noobie developer that has cut their teeth on the elegant Chrome dev tools. Now they need to do some Firefox compatibility work and the first thing that happens when looking at the documentation they see both "Firefox dev tools" and "Firebug" being referenced, each with different use cases and slightly different functionality.
I don't think any other issue is matters as much until you can solidify your efforts and officially support just one set of tools. Once you do that, then I think it's worth talking about all the other improvements that need to be made.
I tried to clarify this in another comment: https://news.ycombinator.com/item?id=5326873 - let me know if I can clarify further.
IMO starting complete rewrite of firebug, in form of devtools, was very wrong. 2 years ago firebug was order of magnitude better than chrome devtools. Now it can't keep up with chrome. But firefox devtools only starts to become barely useful, If all that work have gone into improving firebug, Firefox would be ahead of chrome now.