Yes, I have the Summarit and have used it on the M9, M8 and EP-1. (and M3) I really like it, it is relatively small, and very sharp and very even focus out to the corners.
You have to be careful about focus wide open, as it was tack sharp for me at infinity with all cameras and always bang on with the EP1 since you can focus with the 10X magnifier feature. I wasn't always getting tack sharp hand help with the M9 wide open, to the point I got out my tripod and did some careful focusing tests and it is fine. (It was just me not taking my time focusing and going too fast wide open)
You can basically carry it in your pocket, and if you fit a 35 or 28, and have the 90 it makes a nice walk around pair.
I had the 90 C elmar before, and it is sharper than the C, I had the latest 90 2.8, and it is about the same. I haven't had the 90 APO so can't compare. With pretty clean 1000 ISO on the M9 plus this lens you can do a lot of available light. And the price is pretty good.
happy with mine,
Dave