Agree with you 100% Tino!

When you can receive a 15% discount over and above making the best deal at any Marriott property (making your reservations directly with Marriott), you are doing well.

Also, to answer the question...

You may use these certificates at any Marriott Hotel & Resort (including in Maui), Renaissance Hotel & Resort, Courtyard by Marriott, Marriott Conference Center, Fairfield Inn by Marriott, Residence Inn, and three other types of properties that are operated by Marriott (I do not have a cert. in front of me at the present time). When you can go to VolumeBuy.com and purchase these things for $42.50 for each $50 certificate, you are getting a great deal. Also, it gets even better when you can apply the entire amount toward your Marriott Rewards points and get your points or miles on your affinity credit card.