The problem with that is that Unity hides the menu items until you mouse over the menu bar (at least in 12.04; maybe that's changed since). Mystery meat is the ultimate anti-Fitts.

Of course, it looks like that behavior will be the same in this new mode, which is sort of the worst of both worlds from a Fitts' law perspective.

I think the Fitts' law issue is a bit irrelevant though. If you want to use menu items quickly, you use the keyboard.