I recently bought a 2008 Chrysler Town and Country Minivan at Carmax. It had almost everything we were looking for in a van and had 40,000 miles.
Since we've purchased it, we couldn't have the DVD player installed that they promised us (the Meineke people who install the DVD players for Carmax were surprised we were ever promised a DVD player based on our model), and our brakes needed to be replaced after 3,000 miles of driving it. Carmax was happy to replace the brakes that started squealing 5 weeks after I bought it, as long as I paid them $380.
I feel as though I have been cheated and deceived by this company. So much for their "inspection" guaranteeing a driveable car.
I wish they would have told me up front that the brakes would need to be replaced very soon and I wish I hadn't trusted them and had taken the van to another mechanic for inspection.
My recommendation would be to avoid Carmax at all costs and buy your car at ANY other dealership. I will probably spend more money getting the brakes replaced somewhere else, but I'll be happy not to give Carmax one more cent of my money.