My wife is the one who goes to the trainer partly for accountability, she's not looking to outgrow anything. It keeps her going to the gym. She goes 2 to 3 times per week and I tag along 1 to 2 times a week.
I have a whole gym in my basement with cardio equipment, free weights, a cage, all kinds of stuff. I use it all the time. I go to the trainer because its fun, he's a cool guy, we talk about fashion advice and stuff, and he gets me doing some different types of exercise that I may not do normally.
When it comes to trainers there seem like two categories: ones that you get to teach you basic stuff about exercise and ones that turn into more like a coach who keeps coming with interesting exercises or challenges.