Thanks for the question Pete!
I've been to Gilboa, Haigh, France Park (IN), Blue Springs (IN) and Falling Rock Park (KY). The majority of my dives are in midwest quarries. You are right Pete ... you dive what you can!
There are many advantages to quarry diving. First, it can be a very low stress, low key way to dive vs. a dive boat. Much more like a shore dive. You gear up at your own pace and can take your time. None of the "We're on the wreck (or reef) .... DIVE, DIVE, DIVE!!!!" I'll do that kind of diving a few times a year, but I really like the laid-back nature of quarry diving. It also gives you a great opportunity to meet new divers or to get to know your regular buddies quite well. Second, it allows you to really learn a site well. You get to know where the fish hide and where all the "cool" stuff is located. It allows you to really slow down and focus on the small things. I really enjoy freshwater fish and I prefer the quarries loaded with fish. Gilboa and Haigh are currently my favorites. Third, they are great locations to fine tune and perfect your skills in a relatively benign environment. Don't have to worry about tides, swells, rip currents, etc. Other than the ice we had this Feb/early Mar and an occasionally intense thunderstorm, I've never been "blown out" of a quarry.
Now the downside of course is that you won't find a new, previously known wreck and there are no colorful reef fish, eels, sharks, octopus or other "sexy" aquatic life forms. But if you let yourself be a kid again, it is really cool to pester a crawdad 30' deep on the bottom in your favorite quarry or go head-to-head with the killer bluegill that rule Falling Rock Park in La Grange, KY!