My own personal opinion but they are CRAP!!!! I've gotten free sessions at 3 different gyms and each time the trainer was completely ignorant to fitness. They just followed a set program.
I use one now and I LOVE her. Ten sessions is about $600 and you get one session free. My advice is to scope it out and find one you like first and talk to them before you sign up. I liked her because she was knowledgable and realistic. I have lost 6% body fat since I started and a ton of inches and about 10 pounds (I started in July). Good luck!
I have used 4 different trainers at different locations and liked all but one. I always just told them I want someone really good that's going to push my limits and that I like to do a lot of weight training and I've always gotten just what I ask for. You can also ask for one of their Master Trainers or someone with a LOT of experience. Or just go to the gym and really pay attention to their trainers and decide which one looks good and then request them.
Re: 24 Hour Fitness: Personal Trainers