So thanks to the dev team and the volunteers picking up my and others bug reports at http://firefox-dev.tools/ (I just leave this to the crowd here on HN ;)
I was particularly happy with the Cause column in the network tab that tells me why a particular thing was loaded, which line of javascript or which HTML element triggered it. I think Chrome has had that for a while, but it's pretty recent in Firefox. It's one of those little things that make me happy.
Me too. I seem to recall that back when the Firefox inspector and friends first launched they stated that it would be able to do everything that Firebug did, and that the people who had been working on Firebug were going to join Mozilla to work on Firefox instead. I switched from Firebug to the builtin tools soon after it was released.
Speaking of the builtin tools, I found an old announcement about the Page Inspector 3D View [1] which I recently wondered what happened to since it disappeared not long after it was introduced. Apparently it's available as an addon instead now so you can still have it [2] [3].
[1]: https://blog.mozilla.org/blog/2012/03/13/firefox-adds-new-de...
Unfortunately, tilt (or 3D View) does not work with e10s (multiprocess) enabled. There's a bugreport/issue somewhere at bugzilla: