There are a few interesting new reviews on DxOMark:
The Canon M turns in a dismal sensor quality score, with a dynamic range of 11.2 Evs. That is two f-stops worse than the Sony NEX-6. The Sony (which I own and like, especially for photographing toddlers due to the flip-up waist-level viewfinder (something else the Canon lacks; its screen is fixed)) does everything better than the Canon: color depth, dynamic range, low-light performance.
If that were not bad enough, the latest Nikon 28mm prime lens turns in a fantastic performance, 19 perceptual megapixels compared to just 15 megapixels for Canon’s 28/2.8 (more than one f-stop slower). The Nikon also handily outperforms a manual focus Zeiss 28/2 lens that costs twice as much.
[Separately, I just discovered an amazingly bad user interface feature of my Canon EOS 5D Mark III. When recording simultaneously to two cards, e.g., RAW to the CF card and JPEG to the SD card, if one deletes a goofed-up out-of-focus or eyes-closed image it is deleted only from one card. So you come home with 500 RAWs and 600 JPEGs, for example.]