XSport in Merrifield is good. There are trainers, and you get a fitness evaluation once you start so you can know what type of shape you are really in. The people there are nice, the locker room (I've only seen the women's) is clean. They have tons of classes, pool and tanning, hair salon, etc. there. Oh and sitters on site.
No, I don't work, there, but I've also been a member at Golds and Xsport (in my opinion) is better. My fee is $42 a month, with no contract limit, I can cancel anytime I want.