I used it earlier this year on a flight Nashville to MSP. Had to give the TA the exact code to enter into the system so she could read up on the program. her response was, "Never heard of it before, I have turned hundreds of passenger away unless they had a full fare ticket from another airline. She took the Midwest Airline ticket and gave us seats on NWA. It is a space available program so it is not costing NWA much to take the risk of not getting paid from the other airline....and you might just buy from NWA for them being so kind. You should only do it on a one way or the return trip on RT because if you do it on the outbound the orginal carrier will cancel your trip and you will need to find your own way home...

It can work for you, but make sure you know ALL the rules before you do it.
Wildman