Main problem is that most civilians and cops don't know it is legal. So you go somewhere , concerned citizen calls cops about a "MAN WITH GUN!". Cops show up , might not know OC is legal. Take you down town , confiscate your gun , put you thru the ringer , cost ya time off from work , cost ya money to get a lawyer to straighten things out , get court order to get gun back. Might not be right , but it does happen. And even with a 'permit' , private property owners and privately owned establishments have the right to bar persons openly carrying weapons. Most OCer's , or as I call 'em 'open carry clowns' , do it just to shock and rile people. Like those kids who just got a drivers license and ride around with the boom-boom stereo blaring at 5000 watts.
Believe me , I've been carrying concealed over 28yrs with a LTCF , and still have problems with cops who don't know the laws.
Here's some OC incidents from Mighigan on YouTube. You decide if it's worth the hassle.
YouTube - michigan open carry
There's plenty of websites and forums dealing with OC.