I belong to one. The one I'm attending now is one I used to go to before kids. I liked it because it was handy and I prefer not working out with men. The downside was very average shower facilities. I moved, had a baby and joined another one. It also was good, up to date equipment, good facilities + a creche. Moved again, back to the old one which is now owned by the same owner as the second one. I'm not as happy with this one, despite having same owner. I'd say, like someone else did, it depends on the individual gym. I also found with these particular gyms, that there was no negotiating anything. Try the no-contract thing first, because if you want to get out before 12 months is up, it'll cost you.
I also didn't do classes as that's my preference, but the type & frequency depends on the individual gym.
Good luck.