Carmax? thinking of getting a car from there...i know wrong section?

has anyone ever shopped at carmax? what are the pros and cons? do they take people with not so great credit? if so, do they need a co signer? im looking to get a car from there, but i will not be able to get a co signer....that might hurt me in the long run....but i have ok credit. i only have one credit card and i have been paying my bill every month on time, never late once, and been paying well over the minimun payment. please help. thanks