To me it's a no brainer. If you plan on making Disney World your primary vaction spot at least every other year, then seriously consider DVC. If Disney is a every fourth-fifth year vacation spot then DVC is not for you.
Our first visit was 1986, "off property" and we had a great time. Then we started visiting every year "staying on property". Room prices kept creaping yearly. We had heard of DVC and so finally in April, 98' we looked at BWV and feel in love with it. We couldn't sign the papers fast enough. Yes maintance fees and taxes have gone up every year, but so has the ones on our house. DVC has allowed us to stay on property at a wonderfully beautiful resort, without worring about room cost. Again without all of the math that sometimes I feel gets in the way, it boils down to this to me, DVC is a great buy if Disney is going to be your vacation spot.
All of the kids are gone now, and we are still planning yearly vacations to Disney/BWV. Frankly I'm retiring at the end of January, and I've already made ressies for a big WDW/DL multi week vacation in June using DVC.