I am a 5-TIME CarMax customer and they stand by what they say. I would never buy a car anywhere else. They have a great no-pressure sales team, 30-days from date of purchase they fix anything you find wrong, and yes - you can return it, hassle free (but within I think 5-days and less than 300-500 miles).
My last purchase, they assured me every car had a spare tire. The Elantra doesn't come standard with a spare. So to keep their word, they sent someone to Hyundai, bought me a spare tire kit, a jack kit, installed it - AND, for my inconvenience, paid my $160 hotel bill and toll money. I challenge anyone here to get that kind of service from Hyundai.