Of course it's a money pit, like anything else! DH and I thought things through thoroughly before we bought (I'm sure many here remember all of my annoying questions!!!

). We bought because we saw ourselves in the following predicament on our July 2008 trip:
-DH couldn't stand sleeping in a double-size bed at Pop for 5 nights while touring parks, and neither could I. We're small people (I'm a size 4 and he wears 32 jeans) but we are used to our Queen-size bed at home...what can I say, we're bed snobs!

-DH and I agreed that the right way to do Disney (for us) is to spend 10 nights there rather than 5, and have a few non-park days to relax in the pool, check out DTD and the Boardwalk, etc. We are teachers and have small children, we travel in the summer, so this works for us very well.
-DH and I both loved the convenience of staying on property, and the feel of always being in the middle of the Disney magic, especially for the kids.
-DH asked me where we would have to stay in order to get a room with a queen bed and still be on property, and I told him the cheapest would be the Swan/Dolphin because of the teacher discount. But I also informed him we can't get the
DDP there, and he asked me what about if we still want the DDP (we loved it)? I told him how much a Disney-owned deluxe resort costs, and also the family suite at All-Star Music and he was shocked. He asked me about "this Disney Vacation Club thing". He asked our neighbors, who had bought at SSR. He was starting to be more and more convinced.
-We finally found a vacation we could both enjoy over and over again, and one that was also perfect for our children as they get older, a place we knew we would never grow tired of or be bored with since there is so much to do, and that place is Disney World. I have always enjoyed cruises since I was a teen, and my DH loves them too but he has no desire to do a cruise every year but he wants to go to WDW every other year and I could go to WDW any time so that was perfect for me too!
-Our kids were only 1 and 3 back in 2008 on that trip, so we have their whole childhood to take them to Disney.
So, we decided we would like to go to WDW every other July and stay for 10 nights. We drive down from NYC so 10 nights are perfect for us (we're also teachers and have the summer off with our kids). We choose to go less often but for a longer trip. We looked at
point charts and figured that in order to go for 10 nights every other year and stay in a 1-bedroom, we would need 150 points at BWV. This of course was once we decided on BWV, which was based on close proximity to two theme parks as well as lots of things to do there, plus the lower points needed for a standard view (I don't need a pool view or a view of the BW, and DH could care less about views as long as he can sleep at night). We decided to stay in a 1-bedroom on each trip so that now while the kids are still little and going to bed early, DH and I will have our own space to relax and not have to go to bed at 9:00 (even though some nights we want to!). And in years from now when the boys are teenagers I am sure they will be putting us to bed and stay up later than we do in their own space!

We have our first trip as DVC members booked for July 2010, and we can't wait to go! It would cost us close to $4,000 to stay at a deluxe resort for 10 nights this July! And we would have definitely done that based on our preferences. I'll also add that I can't stand exterior corridors in hotels...and I know it is relatively safe at WDW, but I worry more about bugs getting into the room! It cost us $12,000 for our DVC resale, and maintenance fees annually. This is well worth it to us. It also enabled us to get the DDP without having to buy park tickets through Disney. I was able to purchase our park tickets through
Undercover Tourist (discount site) before the price increase in August, and saved us some $$$. Of course, being able to add the DDP is a current perk that can disappear, but at least for this year, this saved us a little more money.
So right now the plan is to go to WDW in July 2010, a cruise with the kids in 2011, and back to WDW in July 2012. Then, after each Disney trip we can decide what kind of vacation we would like to take in the year in between. By the time my younger son is out of high school (he's only 2 now), we will have completed 8 WDW vacations as DVC members. After that the boys can join us if they'd like to, and if not, DH and I will enjoy WDW as "adults only"!
So, bottom line is, we have enough points for a 10-night trip in a 1-bedroom every other year. If we ever change our minds and want to go every year we can do so in a studio for the same 10 nights. We bought a DVC membership, intending to use it only for WDW trips to our home resort. We always book vacations a year or so in advance, so the 11-month booking window works perfectly for us. We are also making the most of our membership by using it for DVC resorts. Other uses are not so economical, IMO.
Good luck with your decision!!