Simply left alone, bats are more than glad to return the favor. Grounded bats do warrant suspicion though, and should be handled with precaution. Like most creatures, they will attempt to defend themselves. Bats are the same as birds in the sense that they migrate to and from the same roost site . However, I can vouch from my own experience that midwestern bats can and will hibernate through the winter.
Bats are, incidently, the only mammal on earth that can fly.
It's been documented now that bats live a cleaner life than one might imagine. Through much research they are found to be family oriented in that the two mates rear their young in a demeanor similar to humans and that they remain loyal to one another. So, do something for the sake of ecology and play it safe with disease carrying mosquitos. Erect bat houses for your neighborhood night fliers and put more of nature's finest fertilizer on your lawn and garden instead of the attic floor. Say hello to bats, the world's best and safest pesticide.