There is an extensive discussion on this topic over on the budget board -
http://www.disboards.com/showthread.php?s=&threadid=577301. I am not sure if it is because this is a new program or what (it's not
that new), but many people do not know what they are talking about when you try to pay for a portion of your vacation package with Disney Reward Dollars.
If you are booking the trip yourself through Disney you should have no problem, provided your CM on the other end knows what the deal is. In that case, you just use your card like a credit card.
If you are booking through a
travel agent, you might have some snags - depending on the agent. If you use
Dreams Unlimited, you should have no problem. The people at the 800 number you call to make payments seem a little confused about it, so in my case I emailed the information to my agent and she took care of things. The key is using an agency that books travel under your name with Disney and just forwards payment information to Disney - a conduit, more or less. Some travel agencies have the reservations in the agency's name where you pay the
travel agency and then the agency writes its own check (so to speak) to Disney. You can't use your Reward Dollars in that situation because payment is not actually being made to a Disney entity.
I hope this helps - I just went through this hassle last week. We needed to use up some Reward Dollars b/c we are on the gold plan, and it's really hard to spend that kind of money at the park when you are on an all-inclusive plan like that.