We went to one... it was ok, but we definitely didn't love it. And it was so ridiculously expensive. We never joined.
We have gone to Kindermusik every week since DD was 7 or 8 months, though. We *love* it. I've enjoyed watching it shape her into the considerate, tidy, joyful person she is today.
Anyway, definitely do the free trials that Gymboree offers. But don't commit till you've actually given it a shot.
Definitely take Kindermusik up on their offer for a free class, too! (check out Music Together while you're trolling around for free intro classes..
The fabulousness of any of this programs very often depends a lot on the quality of the instructor. GL!