I'm really happy with my M.
Bodies: 6D, 7D, EOS-M, S100
I'm curious - since getting the EOS M, how much do you find yourself using your S100?
I've been having my G10 riding under my seat for several years now as a camera that I could always have with me. I also usually carry a Nikon S800c for the combined camera, wi-fi, and internet. However since getting my EOS-M(s), I don't really use either camera any more because the quality of the EOS-M makes it like I'm shooting with my 60D in live view but in an expendable package.
The way I've come to hold the EOS-M is key for me. Since I'm using it for candid shots at events, I don't hold it up but rather put the camera in the palm of my left hand with the 18-55 zoom ring where I can reach it with my thumb. That leaves my right hand for touching the focus spot and using the menu system. In a tight crowd I use the touch shutter so I simply touch the back of the camera while the camera is somewhat close to my stomach. I never hold it out in front of me like you see phone cameras being used (my open palm position close to my stomach is much more stable - sometimes as low as 1/15 is pretty good for stationery subjects). In this way I'm not being "viewed" as a photographer or even as someone taking a picture. Most of the time, I think people pass me off as "just someone looking at their pictures on their camera" opposed to someone actually taking pictures. I also use the multiple shot function to get the most stable shot.
I've enjoyed this camera and technique so much for candid's that I've purchased the 50mm 1.8 and the 40mm 2.8 pancake (I lost my 40mm some time ago - too small). My favorite lens for getting close in a crowd is the 80mm 1.8 and the EOS-M using my open left palm approach using the other left hand fingers to support longer lenses. Since it is a prime you dont' need the dexterity to move the zoom (there is none) so the fingers are used to support the adapter and longer lens.
In any case I feel much more comfortable in taking candids at outdoor events than with any other of my vertical grip monsters that I really do love but don't fit the "candid" description very well.