The sales guy we met was horrible - he didn't know anything and gave us wrong info at every turn, but they had a great car we were interested in. Despite a terrible sales experience, the service is A+.
We bought a car and brought it to the original dealership for an evaluation. The dealership gave us a list of 5 things that needed repair (from dirty fluid/filter to struts) and an estimate of $2,000. Carmax fixed it all..for free! And they did it quick and were very friendly about it.
I had never been to Carmax before and wouldn't have thought of them if they didn't have the type of car we wanted, but it will be my first stop any time I look in the future. Service surpasses any dealership I've been to - especially when buying a used car with 100,000 miles.
I highly recommend (only 4-stars due to terrible sales person...service gets 6 stars)