They are disgusting. In a town near us, they swarmed to the lighted parts of the business signs, and there were still perfect outlines of the letters (because they didn't land on the darkened parts).
For a few weeks every year, I have to walk through them on my way from the parking lot to my office. My town (and parking lot) are right on the Mississippi River. They stink so much! Our maintenance guy has to scoop them with a snow shovel.