I helped my dad find his last minivan at Carmax. He wanted a Dodge Caravan as he's used to them having two of them in the past. Since I know more about cars than him, he basically was looking for my blessing in a way.
We went to few stores and looked at their inventory. One of them had AC issues (as soon as I turned on the AC the clutch was very noisy), and one may have been hit in the past as the driver side sliding door was sticking out weird.
All in all he was very happy with the purchase he had made. After purchase we were informed that the van was a car rental (which we knew due to carfax).
I purchased my last car at a used car dealership and I had to go through the typical haggling.
I would not hesitate to consider carmax in the future. It was very welcoming to be able to test drive cars, etc without being so pressured to buy etc.
Good luck hunting.