I have sold two cars to Carmax, and I found the same thing. I have not bought there yet, but I would consider it. You won't find a smokin I-need-out-of-my-payments-because-I-lost-my-job deal that you can find from a private party there, and they need to make x amount of profit on each car, but I don't think you'd get fucked there either. You are going to get a car that's in good shape at a reasonably fair price.
Also, I have bought two cars here: http://www.alttx.com/ You basically tell the guy (Richard) what you want and he goes to auction and finds it, then charges $750 plus a fee for the paperwork. I bought a Tundra and Sequoia this way on lease returns and got a smoking deal both times. No complaints at all. It helps to have someone who really knows the auctions and cars to make sure you don't get screwed. I bet there is an outfit locally that does the same thing.