Bought a crossover at CarMax in April, returned it on day 22 after a persistent electrical gremlin. Answering the thread question directly: yes, the 30-day/1,500-mile money-back guarantee worked as written. Full refund, no restocking fee, the mileage cap was the only number they checked carefully. The premium over private-party pricing bought a real safety net in my case. Verify the current terms on your buyer's order — programs change and the paper governs.
CarMax 30-day return: did it actually work for you?
Same guarantee, different outcome flavor: I kept my car, but the 90-day limited warranty covered an AC compressor in month two with zero friction. The no-haggle price was ~$1,200 over the best independent lot, and I've stopped regretting it.