My main concern with this is discoverability - menus are helpful in that they convey a very precise listing of the app's possible actions (when designed well), something that's hard to otherwise come by.

Blender is perhaps the extreme example of this - it has an incredible amount of features, so they can't be placed into menus, and you spend some time learning where (in the hundreds of panels) or which of the thousands of keyboard shortcuts to use.

That said, I find keyboard-driven user interfaces very powerful, so I'm curious to try this out. Fortunately, there's been a way to turn off Crazy Ubuntu Features in most releases if you know how, at least so far.