Bought our Caravan there and traded in an Accord back in ??? '04'ish I believe.
Thought the process was fine and the no haggle approach is good. However, doing comps recently to local dealers with the same cars I am finding Carmax is $2k more than the other local guys. Sometimes it's worth it to negotiate.
I did sell cars for Toyota back in '09 and I do remember one customer coming in with an appraisal from Carmax on a Camry Hybrid that was nearly new, and they showed the appraisal to our GM, and he just laughed and said, "Go back to Carmax and take their offer. We can't even come close to that."
So there you are, both sides of the story.