I possibly should have been clearer.
If it is a good value depends on you and your situation. How do you value your points? How do you value your time? How do you value your money? How do you value your on-site
DVC stays?
If you value your points at the cost of dues (which is how I figure it - the original purchase price is a sunk cost), a cruise is a bargain. If you figure they are worth their rental value, it isn't a deal at all.
If you aren't going to bother with digging up codes or renting your points (I'm not the type) - too much bother or hassle, a cruise is a good value.
If you don't have money or time to pay cash for a vacation, cruising on points is of value. (This is where cruising on points makes no sense to OUR family situation. We can cruise on cash without hardship, and don't have so many DVC points that our family vacations are all tied to spending them).
If you have had enough of the parks for a bit and want to try something different, cruising on points is a good value. (This is also where currently cruising on points is no bargain for us, we have a limited number of points and want to use them to enjoy the parks at this time - cruising on points would result in booking conceirge rooms at the Poly for cash - not a good trade).