My little girl is nearly one year old and has been going to Gymboree for a few months. Taking her to her weekly class is something I look forward to, and she goes most days to the open play sessions with other carers.
Fundamentally it's a clean, safe, fun, and well equipped place specially designed for children of the target age. Although I enjoy playing with my daughter, it can be tough coming up with ways to keep her amused. I like that for at least one hour a week we can have fun together with someone else worrying about the structure.
My baby loves the sessions and several times was almost beside herself with delight, shrieking with excitement and jumping up and down when it was a favourite activity!
Without a control experiment I can't definitely say her development has been improved (maybe she's just getting older?), but the activities certainly look like they're helping.
There is a good spread of activities. Music and clapping type things, free play focusing on gross motor skills, the first beginnings of social play with other babies, and some fine motor work with things like popping bubbles.
Staff are excellent. Admin staff have been helpful in scheduling. The child-facing staff are lovely, remembering my daughter week to week. Very friendly, professional, and happy place.
In terms of value for money, the daily open sessions make it very good. However if it was just the supervised class the subscription would be pricey.