As a previous poster mentioned, the main advantage is that it's a prepaid accommodations program.
My family likes its space, so we'd stay in a one or two bedroom suite whether we were DVC members or not, we will always stay in the deluxe resorts, and we like WDW enough to know that we'll go at least once a year, so it's a decent deal for our family. It's not the deal of the century by any stretch, but it works for us. The DVC rooms are not as plush as the regular Deluxe resorts, and are certainly not up to the standards of the Ritz, Four Seasons, etc.,(they are more like nice Marriotts) but we enjoy them and the relatively less frenetic pace of the deluxe-level resorts.
As far as the perks, we actually don't like daily maid service, so that works well for us. We don't do the dining plan, but if we want it, it is available to us. We like the discount on the APs, and the ability to purchase Tables in Wonderland with the APs. We do, as I mentioned above, like our space, so we can either pay $800-$1000 a night for a two bedroom villa, or prepay for many years of them at a somewhat significant discount and then just pay our annual dues.
It works for us. Whether it works for you is what you have to determine for yourself.