Thanks for this. One little thing : it is not compatible with electrolysis (e10s), the new multiprocess system of firefox. And yes it would be cool to have also 0-9 to trigger it (specially for 9gag !)
For everyone saying F6, Ctrl+L or Alt+D does this:
The point is that you just start typing anywhere, and unless an editable element is selected the text is entered in the location bar immediately. Same result, but quicker, smoother and more intuitive. Windows 8 does the same on the start screen.
Ideal for use with Location Bar Enhancer, where the clickable breadcrumb trail makes clicking to enter URLs and tiny bit awkward. Also, if you use it with InstantFox you can search pretty much any site amazingly quickly by just typing anywhere. Use with Enter Selects and you can get to pretty much anywhere just by typing and hitting enter.
It even saves your bacon if you start typing and don't notice you've missed the text box you want (am I the only one that does this from time to time? :-). The text gets entered in the Location Bar automatically rather than disappearing into the ether. A quick Ctrl+A, Ctrl+X, Ctrl+V and it's back where you want it.
So many improvements to basic functionally in such a small extension.