I've been spoiled a bit, I guess. We lived in Columbus, Ohio for a couple of years...and their zoo is one of the best. It's the Jack Hanna zoo, so you expect it to be good. I have to admit that I was a bit disappointed in the Hogle Zoo on my first trip....since I was comparing it to Columbus. I liked it better our second trip and was able to notice the good things about it.
Prices are very fair $8 for adults, $6 for kids 3-12. You can often find discount tickets, as well.
They have lots of different animals and the new elephant adventure is pretty good. You should definitely check out the bird house and feed the birds. It's a very different experience. The zoo train is a big disappointment. You whisk by a few different animal areas, and the kids never really get a chance to see any of the animals. It's a short trip and really not worth the $1 you pay for it.
It's still a zoo and kids will love it.