I've been an avid gym goer for since I can remember - I had my first membership when I was 15 years old and I'm almost 42. I've been a member at great gym and not so great gyms... The best gyms have all had the following:
* great equipment
* knowledgable and friendly (first name basis) staff with no corporate atmosphere
* hassle free memberships
* energy and atmosphere
Metroflex hits them all for me. If you can't get a good workout here, you won't get it elsewhere. There are people in here with decades of experience and everyone is very willing to help or answer your questions. The owner Josh is super down to Earth and the people there may be serious about training, but everyone is approachable (even if they might not look it!) - simple memberships and 24 hour key fob entry... Music is always up tempo and people are pumped up.
It was a great gym to hit up while I was in Phoenix and if I lived here it's where I'd be training here often.