So here's what happened to me this morning...
Went online to make HDDR at 180+10. I got the time and category I wanted. Went to make the reservation and it wanted my credit card and said it would be charging me the entire cost of the meal. I'm DVC and we will have dining for our trip, but not until we pay for it in October. So I didn't like this answer.
I called 407-WDW-DINE and got a very pleasant woman who told me that what you have to do is book the HDDR and pay with credit card. Then, once you are at the meal you give them your dining credits and they will refund the CC. I didn't think that was a great deal. Last year they just used our card to hold the ressie and we used dining credits when we arrived.
So, needless to say, we are skipping HDDR this year, which is fine since we just saw it in December. At any rate, the deal is that they will charge your card the full amount at time of reservation UNLESS you have dining plan already on your package.