If I was going to go small, it would be the OM-D EM-1 or the Fuji X-Pro1 OMD for the AF, Fuji for the sensor, Fuji desperately needs to come up with the AF performance matching the OMD to win the battle right now, and continue to round out their lens line up. It's very close in my mind, but the OMD would probably win now. A good EVF is still going to be a requirement if I add mirrorless to the bag as I am not a fan of using the 3in screen at arms length; which rules out the Fujis with newer AF. The mirrorless are getting tempting from the standpoint of always being able to have a camera on me, and having a camera that doesn't look pro, so less hassles from others in certain situations.
I'd avoid the M for the time being, Canon has been rumored to be coming out with a newer version that may be respectable, the fist version is getting to a good price point, but it's draw backs would make it a mediocre point and shoot with very expensive glass on the front, as it's biggest draw for me is the EF lens adapter.