Jawad, I too once used a M9 and found it very impressive once writing that the M9 was very close to a baby brother to my P45 at the time. same sensors gave me very much the same color. The only difficulty I had with the M9 was the limitations of the print size thus I sold it and returned to a DF and the ability to switch the back between the two systems.
A lot of what we do is subjective; what works best for us might not work for others. I too don't see me changing sensors any time soon.
Have you decided yet on the camera system? Seems we got sidetracked talking about glass (which isn't a bad thing)...