From a K-01 perspective:
F/FA/DA - autofocus, auto-aperture, all modes supported
A - manual focus, auto-aperture, all modes supported with lens aperture set to 'A', if not set to 'A', then behavior is like K/M.
K / M - manual focus, aperture held wide open in all modes except manual, metering through manual mode with green button only
M42 - manual focus, completely manual aperture, manual mode + manual ISO = green button metering only, manual mode + auto ISO = continuous metering, camera seems to push ISO as high as possible and keep shutter speed around 1/125.
Video behavior also changes with the lens types, but I don't know enough about video to write it up.
Last edited by THoog; 02-27-2013 at 02:03 PM.