My sister and I both had it for 1st bday in Gymboree. I think it's good for the kids who don't have chances to play in such environment before. My son had attended class since 2 months old, so he wasn't too excited, but all the other kids were happy.
My sister had the 2nd bday in the kids gym (forgot the name), and I think it's not suitable for children who are younger. Those who were > 5 years old were very happy though.