I OC all the time...Meijer, Wal-mart, Petco, Kroger, Pet Supplies Plus, Bookstores, garage sales, restaurants, Secretary of State, the Mall... almost never any issues or anyone noticing.
Anyways, a few of the other than normal experiences:
Was at a garage sale looking at some stuff for about 10 minutes - no issues, a bunch of neighborhood kids playing in the yard. As I was getting into my car and leaving one of the kids was saw it and was asking (very loudly for all his friends I'm sure) "Is that a gun?" To which I answered positively, at which point he kept saying over and over "He's got a gun!" - he didn't seem to be scared, but it was obvious he had never seen a civilian carrying before. I was already getting into my car, so I really didn't bother much with it.
Yesterday at Kroger had one of the baggers ask about my firearm and inquire as to the model etc. No issues.
Also yesterday was picking up food at the Chinese restaurant and had a fellow approach me and ask about my firearm. He was from Tennessee, but was living in MI for a while while he worked for GM. He had lots of questions about OC and said he would have had he known it was legal. I told him to make sure he knew all the laws first and directed him to this website. Very nice fellow! I really wish I had not ran out of tri-folds!!