For those with the M9...
Is the "sensor clean" menu option working for you? I can't seem to get it to work. I'm doing the same thing I used to do on the M8...
Select "Sensor Cleaning" from the main menu
I get the message "Press release button. After inspection, switch off camera"
But when I press the shutter release, the shutter does not stay open. It just fires a normal shot, and the shutter closes as on a normal shot.
I must be doing something wrong, but can't figure out what it is.