FINALLY got to use the EOS M in the real world (a show I went to a couple of days ago, would not have gotten in with a 5D3). I just have to give a +1 to the incredible image quality out of this cam - I was pleasantly surprised, even in the low light. It's perfectly fine as an eventual replacement for my SD950IS -
finally, a compact camera that can provide decent IQ!
Its weak point, as everyone has already said, is the AF. It's usually quick enough but on occasion it will hunt (go in and out) when it was in focus already- not sure why/how that happens, the SD950IS never did that- but hopefully that's something that can be tweaked/fixed in firmware. (Didn't stop me from getting a few cool action shots though

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I made use of the continuous shooting mode several times. It's actually quite responsive and coupled with the manual control allowed me to get shots I likely would not have captured with the SD950IS.
The 22mm lens was a bit wider than I would have liked for many shots (provided a good perspective when the action was close, though)...I would really like to see a ~50mm fast prime lens that's either the same size as or just a little larger than the 22.
But comparing to the SD950IS - completely blows it out of the water in IQ, color reproduction and resolution. Plus I can shoot RAW and my workflow is the same as when I shoot with the DSLR. I still carried the SD950IS with me and used it when I wanted to get a little closer...comparing the pics, you can EASILY tell which camera took which shot.