In a nutshell, DVC saves a lot of money if you typically stay at Deluxe resorts and visit WDW at least every other year.
If you like to stay at Pop Century or All-Stars and only travel in the off-season, then DVC may not be for you, as the annual dues will probably be similar to a week at the Values in the off-season. However, that is at today's prices. In 30 or 40 years, a night at the Pop will be several hundred dollars, but the point values are basically fixed for DVC which means DVC is almost inflation-proof (taxes and maint fees notwithstanding).
But, even if you like Pop or All-Stars, you should stay in a DVC to try it out. Renting points or booking through CRO are the two easiest ways to stay in a DVC accomodation. You may just get spoiled!
If you only travel sporadically or less often than every other year, then DVC may not work for you, since you get points every year and have to use them or lose them. With banking and borrowing, points effectively have a 3-year life.
If you only visit on weekends, then DVC will likely be more expensive than hotels because the weekend nights are higher point cost than weeknights. (However the caveat about today's dollars applies here too).