I belonged to Gold's Gym for three years and worked out during lunch everyday because it was right next door to work. I now belong to Planet Fitness, which is closer to my home, and I workout first thing in the morning everyday.
Planet Fitness is a bare bones gym. No child care, no pool, no basketball court, and the classes offered are sessions for about five people for different types of training for abs, chest, mostly weights type stuff. BUT - it costs $10 a month and its open 24 hours. Gold's was costing me $35 a month plus a contract (2 years I think?), and I never could make their classes fit into my schedule. The other difference? Planet Fitness has trainers for about $25 a session and I paid $60 a session at Gold's.
If you are the type of person who can spend two hours at the gym and take advantage of the pool, classes, steam sauna, hot tub, child care, etc....then its probably worth the $35 a month. If you have to get in there and get out, like me, Planet Fitness is the way to go.