You sure you want to start this? :ROFLOL: The value of DVC has been debated here more than a few times, and it can be a very lively discussion. It really boils down to personal circumstance and vacationing habits. Here's how it works...
When you buy a DVC, you are buying into a certain number of annual points. Direct sales from Disney start at 160 pts. Those points are used to rent your room. The point cost to rent a room varies based on season, room type and resort. For instance a 1 bd. room at BLT with a MK view in October is 288 pts. The same room during Christmas week is 466 pts. Room sizes vary from Studio, which is a little bigger than your average hotel room but has a kitchenette, to the grand villa that sleeps 12 people and has a full living room, dining room, and kitchen.
Points can be banked to the next year, or borrowed from the following year, so the max number of points you can use at any time is 3x your annual amount. So if I banked 200 pts from '09, I have 200 pts from '10, and I borrow 200 pts from '11, I could get a room for up to 600 pts. Pts expire after 2 years, even if they've been banked, so I need to use the '09 pts by the end of '10 or they're gone. The best value for spending DVC points is at the DVC resorts, but you can also trade them for Cruises, stays at the non-DVC Disney resorts, Adventures by Disney, etc.
You pay a certain amount per point plus closing costs when you buy. You also pay annual dues on your points. Dues vary by resort, and are used to pay the resort upkeep and taxes. There's a list of current dues by resort, but I don't have it handy. Mine for 200 pts at BLT are about $650/year. The value of DVC comes from using the points over the long term, to get vacations for basically the cost of the annual dues. So if a 1 bd room at BLT costs $300/night, and I vacation for a week annually, I will "save" $2100 (room rate) - $650 (dues) = $1450 savings for that vacation. Mind you that you need to recover the up from costs of the DVC so I have about $18,000 to "save" before I break even. You could also recover the up front costs by re-selling the DVC so there's value as well if you need it.
So the question of if it's worth it comes down to your lifestyle and vacation habits. The driver behind me getting DVC was 3 kids. I always needed to get 2 rooms, or upgrade to the villa's every trip. That's an expensive way to travel, so DVC is cheaper for me. If I was single, and didn't mind staying in the value resorts, DVC wouldn't have been worth it. Others will argue that the Studio upgrade from a value resort makes it worth the costs. It's really a personal thing.
Well, I'm out of coffee, and need to get to work. Hope this helps you understand a little more than before.