The MUP I ride on is in a metropark and is littered with STOP signs. These are at every driveway to every parking lot and even at interesections that have traffic lights. They are illegal, imo, and no one pays attention to them.
My biggest worry is the driver of the car who enters a driveway, going to a ball field or parking lot. He won't stop, so you have to be on the look out to the road side of the MUP. Sometimes your vision is blocked by trees.
The other frustration is that some cyclists ride in the middle of the MUP. Get on your frickin' side!!!

If I had a road bike, I'd be on the road. But the MUP isn't too bad. There aren't too many driveways. Also, lots of the MUP follows the river and there are many areas that go deep into the woods, away from the road. That part is a lot of fun.