We've always had a few in this house; they've generally made their home in the garage rafters safely tucked away from view. Every now and then we'd see one, bouncing up against the window into the garage in pursuit of insects. (Really, don't ask--I know it's not normal to have a window looking out into one's parking structure, but that decision was made long before we moved in.)
It's not a huge deal to me that we have bats in the garage, though it does get annoying to find bat poop and pee all over everything that lives out there. The bad part is that somehow they seem to occasionally find their way into the house, and once they're in, they can be a bear to ferret out.
It's not so bad if you catch them when they're flying; Emily's broom handling makes Barry Bonds look like a sissy. But they only fly late, late at night, and hole up during the day. If you're lucky, you can find a concentration of droppings and locate their hidey-hole that way. Or you can make a bunch of noise and if you're lucky they'll hiss at you in return. But mostly, you just have to resign yourself to the fact that while you're snoozing, they're running around your house, dancing techno or hunting insects or whatever they do. But mostly pooping and peeing.
So they're back, as witnessed by the spoor left in our under-construction family room. And I feel like Jack Lemmon did in Grumpy Old Men, that these Walter Matthau-esque bats are the bane of my existence, that no matter what I do, no matter how many I catch (and I do catch them--in fact, I've got one in a jar in my freezer as I type), they'll always return to laugh at me.
At least I haven't gone so far as to do what some friends of ours have done. After finding bats in their house, and after learning that they can carry rabies, they went through the entire sequence of rabies shots. Yikes.