I have used it successsfully twice now (for 2012 and 2013.) Both times was for car rental with Avis. I first found the car and rate I was after online, then called PTS and said, "I wasn t to sue my travel credit. This is the agency, this is the car, and this is the rate quoted for these dates." On both occassions PTS came back with an even cheaper rate, and then applied the credit.
Also, on both occassions the credit posted on my account within 24 hours of booking with PTS.