We have used Negril One Stop twice and have yet to use the discount card. The card is dated (for the exact dates that you are at at Negril One Stop property) so it is not a "forever" card. Discounts are in the 10 to 15% range. Some of the places on the list may not even be in business anymore.
Our previous experiences with Negril One Stop were positive so we just used them again to book hotels for an upcoming trip to Negril and Treasure Beach.

Regards,

Bob