I looked into this several years ago. My conclusion was that it is not worth it.
Ther flights that were available were very limited. And you had to go for one week or two weeks exactly. No changes permitted. No checked luggage allowed. And you had to pay for the ticket, not the full price, but a good hunk.
One guy in the business I talked to at the time told me that it was only a good deal for student types who didn't much care exactly where they went or when they went. And even for them, deregulation had cut international fares so much it really wasn't worth it.