Interesting question! We started with Oli when he had just started crawling and I really think it helped develop his spatial awareness and he seemed to enjoy some aspects of it. We started in on class but then the class got too small so we were forced to move to another one, which was a lot bigger - I dont think he enjoyed that so much. My little one loves exploring and doing his own thing, but gets quite grumpy when you try to "make" him do something that he doesnt want to do.
Overall I think it was positive, although we are now going to Tiny Tots Gym a the YMCA, so will see how we get on with that one.
My only negative feedback would be that the lady that runs it can be a little "harsh" and "stern" sometimes. My little man didnt really like her very much, so that made it interesting sometimes!