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We have it in the sidebar but not the tree. Its coming though: https://bugzilla.mozilla.org/show_bug.cgi?id=920141

Do you see the live editing of JS and on save they getting executed in a VM? I think it is pretty rad and not present in FF devtools at all. Please correct me if I am wrong.

Firebug gives you the option to toggle all pseudo states for an element and edit its CSS. IMO Firebug and Chrome's dev tools still lag behind Firebug's.

This might be Nightly only. But in the Inspector pane of the Firefox dev tools you can right-click elements to set their focus/active/hover states. Doing so will also update the pane to the right showing any state specific rules that now applies.

That's good to hear. I have been using Firefox Nightly since quite a few months now. It's impressive. :)