We have done this once, and we are doing it again. On our first trip as
DVC members we useed some of our points to stay 4 nights at the Poly (This was for December 1999 and all of the DVC resorts were full because of the expiration of the free passes - long story). Anyway this was during a low season (week after Thanksgiving) and it was 97 points for the 4 nights. We had a room on the second floor of Tahiti facing the Magic Kingdom. We are staying at the Animal Kingdom Lodge for part of our next trip and we have a Savannah view room that is costing 29 points per night. (During the same trip, we are also staying in a preferred view 1 bedroom at the Boardwalk for 22 points per night, so you can see how it is not as good of a value as the DVC resorts.)
Anyway, it is very easy to book these rooms, you just call Member Services and book them just like you book the DVC resorts.
One note: When you make a reservation for a Non-DVC resort, those points get converted from "Vacation Points" to "Reservation Points." These "Reservation Points" cannot be used for DVC resorts and can't be converted back. So if we decide not to visit the Animal Kingdom Lodge, we have 116 points that we can't use for DVC resorts. (We could use them for a different non-DVC resort though)