I've had issues with PTS agents booking the FHR third night free deals not knowing whether the price they're quoting are for the first two nights or are the average rate for the three nights. Obviously it makes a big difference, but the phone agents don't seem to understand or appreciate the difference in cost.

Similar issues arise with Starwood third night free deals, which require use of a special rate code and tend to be nonrefundable. There it's especially true that you can often find better rates without the third night free feature. However with Starwood what is explicit is that there is a rate specified for the first two nights, so that if you depart early this is what you must pay; they state the the free night will be applied at check out, assuming that you really did stay three nights.