I think it's a great gym! Good range of classes, good cardio facilities, and clean, pleasant changing rooms. The Fusion Card also allows you to access a number of alternative gyms within Southwark - Peckham Pulse, Seven Islands, Brockwell Lido, etc, all of which offer different facilities. The booking system is better now than it was last year - I've not been refused a single class since November-ish, and I tend to go to around three each week. Personally, I've never even seen a teenager in there, but agree with comments about Saturday/Sunday mornings (when you can wait for up to 20mins for a treadmill) and Friday nights (when you'll struggle to get into the weights lounge for all the 20-somethings trying to pump their biceps before going out on the pull).