I'll be taking the April MCAT and took the TPR course over the course of the current semester. Some of the instructors were better than others, but I think that what I basically paid for was to have someone tell me what I should understand, what I should memorize, and how to take the test (strategies). And of course the ton of practice material and diagnostic exams they give is definitely a big plus. The review books do contain some errors but are generally a good resource, and outline very clearly what you need to know.
If you're really organized and can make a study schedule and stick to it you probably don't need to pay >$1k for a class, but it's been helpful for me so far. The course was recommended to me by a friend who improved her score by about 10 points, and as of the latest practice test I've improved by about that much too. The cost, in addition to the $1k, is having no social or leisure life for the semester. Basically all I did this semester was schoolwork, MCAT studying, and a couple hours a week volunteering. There are a couple students in my review class who are working full time, and it's basically the same for them; work, MCAT studying, and MCAT classes are all they do.
Hopefully it'll all pay off though.
Of course, I have yet to take the actual test so take what I say with a grain of salt.