We have been taking our son to The Little Gym since April 2005, and it is worth every penny. He has more fun that I ever thought he would, and he gets to run off his energy.
There are different levels for the classes per age range, and at his age, we (his parents) get to be involved during the class.
The classes are not strictly structured meaning that they don't "make" the toddlers do things that they don't want to. This makes the class more enjoyable. They have no problems with kids who can't sit for long or have a short attention span. Young kids have a short attention span and you can make something not fun by being too strict. They actually encourage the kids to explore around the gym and I believe this enables young kids to learn more. Toddlers learn differently than older kids -- through exploration and The Little Gym encourages that.
They do have all of the classes structured in the manner that there is a routine of what happens at the begining, middle and end. This is great for toddlers and they love to know what is coming up next. The songs are silly, so all the kids love them and respond positively to them.
Each week they learn a new skill. Sometimes they get it and sometimes they don't. As long as my child is having fun, I honestly don't care if he "gets" it. It is all about being a kid and having fun!
My husband and I actually enjoy going to the class and watching our son have a fun, smile, laugh and have a good time.
The instructors are very caring and friendly. I would highly recommend you at least take a trial class. Your child will love the balls, bubbles, parachutes and jumping on the air up mattress.