I don't think your main problem will be the window managers (or even desktop environments). All of the ones I've worked with support numerous keyboard shortcuts, and some are considerably more extensive than what windows sports.

Your problem will be the applications. Some are good, some are bad, and many are nightmares. Even with things like the HIG many applications have shortcuts that are inconsistent, and some have no shortcuts at all.

In fact, the trend seems to be getting worse: a lot of the applications are trying to be all mousey, and forgetting about keyboard users. Witness the open file dialog for Gimp 2.2, or Xfce's file manager, or image viewers that are actually keyboard-friendly (xzgv is about the only one, and not by much).

A major problem is that although a lot of OSS advocates scream "choice, choice, choice!", quite often there is no choice, since there's only one semi-decent program, and all the alternatives are incomplete alpha-level software. So you're stuck with whatever keybindings they have.