We love our DVC membership, but I agree, it doesn't really save us money because if we had not joined, we would have stayed at the value resorts instead.
What it does is give us the chance to stay at Deluxe resorts when we never would have done so on our own.
It also 'ties' us to vacationing at Disney at least every other year. This may not be a good thing for people who would rather not go that often. We love Disney, and I can't imagine not wanting to go at least every other year (we like going a couple times a year actually, but it is getting to expensive to travel there that often).
We bought 150 points, and at first you feel like you really want MORE points and when you first stay there you want MORE points, but I am so glad we didn't do that because our 150 points are paid in full (we just pay monthly dues which is around $55 a month) and we can skip a year and not end up with too many points to try to use up (we have never rented points, but that is what some members do when they have points they can't use).
I agree, the DVC boards will give you more information, but remember they (we) are biased in that we all bought into DVC and we all love it (or we wouldn't be hanging out on the DVC DIS board).
DJ