I took advantage of this. If you're booking multiple nights, the most expensive night is the free one - and they also don't charge a resort fee for that night. I got five nights over Labor Day weekend for ~$730 all-in, inclusive of taxes and resort fees. The free night saves well over $300 when factoring in the rate, taxes, and resort fee (the rate for Saturday night was $249 plus tax). And the reservation can be canceled up to 72 hours prior to check-in for a full refund. For comparison, I'm Caesars Diamond and the same dates are $200 more expensive (even with no resort fees) for an inferior room at Caesars Palace.