I agree with some of what has been said, but post-bac programs can still be very helpful. It depends on what you need...if you are a complete non-traditional student, and need all of your pre-med requirements, then a post-bac is an excellent choice. In fact, that's what it's designed for.
I think it also depends on the strength of the particular program. Not all of them are looking to just make money off of you. The program I am in right now offers excellent opportunities to be involved in clinical and research experiences, and there are courses/dinners/seminars throughout the semester all specifically held for the post-bac students to give us an even better introduction to the field of medicine.
That being said, I checked out some other schools as I was applying (ex: USC) that "said" they had post-bac programs. When I looked further, though, I realized that there's not really a structured program or any good academic advising. Basically, you just go to their school, give them your money, and take the classes you need. In this case, you're probably better off on your own.
I guess it's your choice. Do you chance going it alone, or do you want excellent advising and support from other post-bac students that are in your situation also? My experience has been an excellent one, with great advising, and no doubt that I will get into medical school. The directors of my program ARE NOT making big money off of us. They have vested all that they have into our success.