It can be worth it if you can be honest with yourself and say yes to the following:
1. You plan on going on at least 10 Disney
disney vacations (aulani, Vero beach, South Carolina, Disney world or
Disneyland) over the next 15 years.
2. You don't have a problem planning trips far in advance... Like between 7 and 11 months before your actual trip.
If you can honestly say your cool with both of those then there is potentially some value for you. The next question is tougher:
Knowing all the resorts are really nice, how important is staying at a specific one at a specific time of year to you?
Some resorts (grand cal, beach club, etc...) are hard to book at even 7 months before your trip if you plan on going in oct- dec. If you just have to stay at one of the preferred resorts, you'll absolutely want to buy there (most likely forcing you into a resale purchase since only aulani and polynesian are available direct)... But just know you'll need to book your room between 11 and 8 months before your trip.
If that isn't you and you want to get around to different resorts, don't have a specific place you want to go all the time, or don't plan on booking a year ahead of time, your best value per point is saratoga springs. The initial buy in is low, about $80 per point, the dues are among the lowest of any resort and it still has many years left on the contracts so you can either use it for a very long time or can expect that resale values will be pretty good in 15 or 20 years.
Buying at saratoga springs will pay for the 45 years of vacations in about 8 vacations (considering that you usually can get about 25% off rack rates).
You can even find some contacts that are cheap enough you can actually make a profit over your annualized costs just by renting points. Search around the boards here, consider what you actually want out it and do whatever feels right. Best of luck to you!