If you are doing the 100 point add-on at SSR, then you can get the $8 incentive (the minimum for getting the $8 off is 100 points). Someone had mentioned that they might let you exchange the $8 off incentive for additional points. Also, depending on the UY of your contract, you would either be able to get the 2005 points, or 2004 points.
If you are trying to add-on at any other resort, there is no incentive (except being able to get either the '04 or '05 points, again depending on your UY).
Give your guide a call, I'm sure he/she will be glad to fill you in on the details of what you can do.