So, not directly on point, but I just called the Platinum line and was told that the stay 1 night get 1 night free offer is usable with the "Summer Sleepover" rate (OTP). I just booked the Philly Downtown Marriott for next weekend - the OTP rate of $179 is higher than the general rate of $159, but for it we'll get breakfast for two (they said that would only be for 1 night) plus the $100 bonus buck coupon and the $50 united coupon.