My experience has been limited to dSLR's (oh, and the Oly E-P1) but I have never used a manual focus viewfinder camera. My last manual focus camera was the Canon FT-QL! But at least it was through-the-lens focusing.
I don't understand how one focuses a viewfinder camera's lens. How do you know when you have accurate focus? What do you see inside the viewfinder (I know you see an outline of the frame)? Small errors at wide aperture can create a disaster so there must be a way to get it right.
A corollary question: can one focus quickly? I can't imagine that it's anywhere near the speed of autofocus on a dSLR.
Also, is the M9 introducing a new technology to assist focusing?