What are the cons? Why isn't it higher ranked on peoples' lists?
I live here in Indianapolis, and so I take my 6-year-old to this Zoo at least once a month. I know this Zoo like the back of my hand!
Moebelle's assessment is pretty accurate. The Zoo isn't really "small", but just has a small number of exhibits. The exhibits it does have are large and very much above average, exhibit quality-wise, but the larger size means there are fewer animal exhibits on site. The zoo doesn't really have many "galleries" of smaller animals, except for one small room with about 8 or 9 snakes.
One thing that many ZooChatters dislike about our Zoo is that it is very much aimed at children, which is why my 6-year-old loves it so much! There are 3 very popular animal shows, featuring dolphins, macaws, and dogs. There are also some unique petting and feeding opportunities, including a big shark-petting room, giraffe feeding, flamingo feeding, and budgie feeding. (The shark-petting room may be the most popular place in the Zoo!) There's also a number of fun rides for kids, including a sky ride, carousel, train ride, and "family" roller coaster. As I said, the kids love all of this, but some purists think this is all unnecessary, especially if they're touring the Zoo without kids.
The "Cheetah show" is actually just a keeper talk, but cheetahs are a big deal in the African area. They have two big yards with 2 cheetahs each, with great viewing of them. There's also a fun thing for kids where they can "Race a Cheetah" (actually an electronic cheetah, kids find out how far they can run before the cheetah passes them).
The newest thing at our Zoo is extensive exhibit for about 30 long-tailed macaques. Eventually they're hoping we can watch these aquatic monkeys swimming from an underwater gallery. Near to these monkeys is a very nice walrus exhibit, one of the few zoos to exhibit them.