Rated 4 out of 5 stars
This is a fantastic idea, but dude, seriously, Shift + Backspace. I don't remember if you can use Backspace as a back button in Firefox, but you definitely can't make it the left mouse button, although I like the idea, but it isn't practical. On top of holding the left mouse button to move tabs, I also double-click to close them using Tab Mix Plus. You two need to high-five sometime and *really* make a cool add-on together.