Keepers.....

Interesting question!

I looked back at a few vacations and found that I typically delete 25-30% of the images I take, for a 70-75% "keeper" rate.  I post from 15-30%.  As others have observed, the rejects are not so much misfocused or misexposed as they are inferior composition or timing relative to the ones kept.

I don't see much difference between my M4/3 and my previous compact camera.  I suspect that keeper ratio has more to do with one's attitudes toward shooting, discarding and sharing than it has to do with the camera.