We used to go
I took my ds (2.5 yrs) while I was at home on maternity leave with dd's birth. He was 20 months when we began going, and about 26 months when we stopped (because I went back to work). We had a good time, but I never felt any great need to make ds follow the "curriculum". My feeling was that we were going to allow him some guaranteed play time with other kids his age, and later, as I got to know and like some of the other mothers, it became my social time too. I really liked the teacher at that particular location, but I could see how the teacher can make or break the group. Another advantage was that I purchased an unlimited pass which meant we could go every day if we wanted to, and we ended up going 4 days/week. A disadvantage is that he quickly grew out of the equipment. IMO, it's really meant for young kids just learning to climb and he quickly mastered everything and then grew bored, which led to some aggressive behaviors here and there. Now we go to My Gym http://www.my-gym.com
. It's meant for kids up to 9 years, so he's much more fascinated and challenged by it. I think the disadvantage to this program though is that where we go, you pay for sessions of one class per week, and you don't have the opportunity to go as many times as you want, and it's not cheap (neither is Gymboree for that matter, but it's cheaper than My Gym). But ds likes it and I do too. However, next summer, I'll take dd to Gymboree (she'll be 14+ months) because she'll just be learning to climb and we can go a few times each week, and mothers from my ds's class have children dd's age as well, so I'll get to play with them too.
I can easily see how the other mothers in the class can also make or break your experience too. For example, when we began My Gym, I had ds enrolled in a Friday a.m. class and I was really grossed out by many of the other mothers--they'd say things to each other like, "Great! Now you've got your quality time and outside time done for the day!" How disgusting is that?!:yuck Then I switched him to a Saturday a.m. class and I'm much happier with the other mothers. I hope this was the kind of information you were looking for.