DVC is a good program, but it is not for everyone. I'm happy enough with it but am not a big user like some of the people on this board. You need to ask yourself some questions to decide if it is for you.
1. Can you afford it? DVC is a luxury (as are vacations to WDW). Make sure you can pay for point the points, the annual dues and the costs of the vacations without straining your budget. I personally would not finance the purchase, but I am both in the position where I don't have to and many others are comfortable financing. It does increase your cost though.
2. Will you be going to WDW at least every other year? You need to use up your points as they expire (you can bank your points one year). If you are planning on returning regularly, DVC might be for you.
3. Do you normally stay on site in deluxe or moderate resorts or do you want to upgrade your accomendations? If you are perfectly happy off-site or in value resorts, you can probably go cheaper than DVC.
4. Will you be using your points at DVC resorts all or most of the time? This is where you will get the most value. The trade outs are nice for once in a while, but I wouldn't buy DVC if you are planning on trading out alot. While the number of points to stay in a particular type of DVC room in a particular season won't change, the number of points for a cuise or to trade out to other hotels will likely go up over time.
5. Can you plan your vacations in advance? You can book your home resort 11 to 7 months in advance. At 7 months you can book any other DVC resort. To get certain types of rooms you may have to book close to 11 months out. And to get other resorts at certain times of year, you need to book right at 7 months. Other times of year have less demand, but even so it is typical for it to be full several months out. While you can get rooms with short lead times sometimes, DVC would not be a good match if you often want to take last minute trips.
6. Are you weekend light or neutral? Friday and Saturday nights take more points that weekdays, about double. Long weekends can get expensive.
This just gives you some things to think about - DVC could still be right for you even if you don't meet all the above criteria - just make sure you understand what you are buying and its costs and its value to you. Some people are OK paying more to be "forced" to take a vacation every year.