DVC certainly is not the cheapest timeshare around - but - IMO - is still one of the best. (My FIL has 8 non-Disney timeshares, through various networks and companies - and none of them have impressed us like DVC has - and that's NOT just because of my love for Disney either).
It IS a timeshare, and you WILL have annual dues, or maintenance fees. Every member contributes based on their level of point ownership. These fees go to cover the costs of staffing the resort, maintenance, insurance, repairs, transportation, property taxes, etc, etc. (Note: All cash guests at the regular resorts also pay these things through their nightly rate & taxes whenever a room is booked and used - you just pay for the nights you use and that's that). These dues do get paid annually, yes. And they do go up over time, but historically (in the 20 years since DVC started), the rate of increase has ranged from 2-3% annually. Cash rates for the WDW resorts have gone up 3-5% annually - for comparison's sake.
Even though it IS a timeshare - it's better, as Chris said, to think of it as pre-paying for your vacation accomodations. Once your initial purchase is paid for, you only pay the dues each year. Most people "break-even" in 5-7 years of trips. However, if you go more often, as we do - you'll break-even faster. We've enjoyed DVC stays 15 times now in the 3+ years we've been members, and we've surpassed the break-even point. It's nice not to have to pay for our accomodations again when we go. Sure I'm paying dues, but they are way less than if I were to take my family of 5 for a single week. All told, all of those visits added up - if I had been paying cash (first we wouldn't have gone as many times - sure we would have gone, but not quite as often), there is nearly a $25,000 difference between what our points cost us, and what we would have paid cash. Even factoring transportation, tickets & food in to the equation I've come out ahead since not all of those trips were full on family trips, but part of the family or solo trips.
As a family of 5, our options increased tremendously in where we can stay. We aren't limited to the few resorts that WDW offers for us all to squeeze in to a tiny hotel room. With a 1 bedroom, we get a washer & dryer in the room, and a full kitchen. We can cook our own meals if we so choose. We also get a 2nd bathroom in the room, at the newest DVC resorts - AKV Kidani and BLT.
One thing to consider of course, is that with DVC, you are paying for accomodations... not tickets, and food. You can't get a package like you can with a typical cash resort package. BUT - as a DVC member you can add the dining plan (if you'd like), for as many as or as few nights as you would like during the stay - it doesn't HAVE to be every night of your stay any longer as the cash resorts are. Many DVC members, like us, choose to order groceries and have them delivered. We can also get the TIW (Tables in Wonderland) card - which saves a bunch of money over using the Dining Plan.
As DVC members we can get an Annual Pass, $100 less than anyone else can too. That is huge when you multiple times in a year. And there are always various discounts and perks available as well, that can help save money on different things - of course - only if you were going to buy or spend money on those items anyway. Example - I can save 50% on the cost of minature golf... one of the things that we'll be doing this week; or get $4 off (basically 10%) of the cost of a water park ticket. Nothing stupendous, but if you would be doing those things anyway... those little perks help.
DVC members can also use the DME service just as regular cash guests, no charge out of pocket (I'm not positive, but it could be included in our dues, just as the cost of DME is actually built in to the nightly rate cash guests pay).
It took us 12 +/- years to finally come around to the decision that the time was right for us to join. I first looked at DVC in 1991, but as a single guy living in CA, it didn't make sense for me. In 1994 on our honeymoon, we toured and I wanted to... but the DW didn't. We toured in 2006 and 2007 before finally signing on the dotted line. Since then - there's been no turning back... and I don't regret it at all. Prior to DVC we never would have gone to WDW and done a no-parks trip... but thanks to DVC - we can. We can enjoy the resort & its' amenities... something we barely even thought to do when we were just there to see the parks. But having gone back so many times - they are great to enjoy, but honestly, aren't all the world has to offer. AND... we'll be back - so going to the parks next time is always an option.
DVC is clearly not for everyone. The purchase price per point continues to rise. I WISH I had been able to pay what Dave did for his points... but I didn't. I joined when I joined, and we paid what we paid. But even still - I don't regret it. We've not only regretted it, but we've added on 7 times, and currently have more than 600 points. We'd like to add the VWL to our portfolio as well, as I want that home resort advantage for December trips - but so far don't have the blessing of the DW yet.
I've recommended it now to about 8 different folks - 3 of whom have joined too. You can join directly through Disney - by purchasing the minimum of 160 (though there have been offers putting the minimum at 100 for certain resorts like Christian got)... or you can purchase a "used" contract via resale. There is no requirement on the number of points to purchase when you go resale. I know several people who picked up a small contract (25 - 30 points) via resale to get in to the system, and then be able to add-on directly from Disney, where the minimums are 25 points cash, or 50 points financed. (Getting past the direct buy-in hurdle has been a concern for numerous folks I know).
I hope all of this helps. If you have any other questions I can help with - you can always PM me - though I'm happy to respond or answer here as well.