Having grown up in the QCA, I find it funny that people vaction there. It just never seemed to be much of a tourism spot.
Anyways places to see and things to do:
If you are there in July the Bix fest and race are quite a sight to see. Also in Rock Island (accross the river from Dav) The District downtown seems to have a festival of some sorts every weekend plus a good night scene.
Blackhawk state park in rock island is a neat historic place to visit. Also Scott County park in davenport is a really nice park.
Have fun!
