SharonS is right in that a single person doesn't pay 2x fares. I was just trying to keep my first answer simple. For a single person they back out the costs of meals, and I believe port charges as they are not actually being used by any second person.
We've taken the 3-day and the 7-day and thoroughly enjoyed them both. However, we paid cash both times, did not use points. Depending on seasons, discounts etc., we've gotten both cruises cheaper than what we consider a point value. For example, for the current 7-day special, if you value a point worth $10.00, then the 106 point cat 10/11 cruise equals $1060/person. If you can get it for cash for less than that, you might consider that route.
On the other hand, if you only have so much time available anyway that you couldn't take a cruise and also have enough time to use all your DVC points separately, then use your points for the cruise. In September a 1-BR at VWL or preferred BWV is 200 points for a 7-day week. By comparison, 212 points for 2-people for a 7-day cruise is a pretty good deal.
Caskbill