Upload & Sell: Off
According to photos I've seen online, the new Canon EOS M camera (when fitted with the new 22 millimeter M lens) is pretty close in size to Canon's own G1X. The EOS M has a slightly larger sensor than the one in the G1X, and of course the owner can add the M-series18-55 zoom - and any Canon-compatible EF or EF-S lens with the adapter. The little 22 millimeter lens (roughly a 35 millimeter equivalent, I believe) is an F:2, faster than the widest aperture on the G1X's built-in zoom lens.
But neither one is as compact as the battered Canon G9 I've been carrying in a belt pouch for years. And when you add the new (and, in the US, optional at extra cost) EX Speedlite and the M zoom, or any Canon-compatible lens with the adapter, the EOS M becomes even more of a brick, requiring some sort of bag or large fanny pack to carry the extra bits around. It's no EOS-1D X, of course, but it won't fit in a belt pouch, either.
By contrast, the G1X, even though a bit larger than most predecessors in the G series, is an all-in-one package, with a built-in flash (with its admitted limitations) AND a hotshoe that can accept any Canon flash (though some of those flashes are larger than the camera!). And it has a feature I find very useful - a fully articulated LCD finder that allows accurate framing of both vertical and horizontal photos from low or high angles. The EOS M doesn't have that, though it may show up in future models.
At the moment, and for the way I use a small "always with you" camera, I'm more tempted by the G1X than the EOS M. I would be interested in your reaction to the new camera.