Moire would be a real concern for me, I shoot aerials often over Cities, a clear day and views across a city at infinity will produce the right frequency for moire somewhere. I proved that with the Kodak SLR/n.
I have never owned a M of any kind but I do have a desire to own one, not because I can make a list of things it does better or worse than another camera, but because of the sum of what it is. I can appreciate the things Leica gets right, maybe because after too many decades of using film and digital my priorities are the basics and not the add ons. I'm sure you could get a degree in understanding the pro's and con's of Canons AF system, when to use this setting or that setting, God knows I've spent a year working on the permutations and hours standing out in the street at low light figuring when it will or will not deliver a focused image and to be honest I don't know much more now than I did when I started.
I am at least now pleased with Canons range of wide angle lenses and after weeks of searching I now own a 24mm mkII.
If I was a Leica owner the choice is much wider of decent optics.
I like the size, I like the control, I like the simplicity, I like the quality, I like the lens choice, I like there not being a mirror, I like the history of the Leica. I don't like the price, neither do I think it is over priced. Wether point for point a Nikon or Canon can beat the M9 on file quality is neither here nor there, they are completely different tools.