We bought in last year because they built BLT and we knew it would be the resort for us. We had been going almost yearly since 1994 but didn't like the locations of the other
DVC resorts.
We love being members. It is so great knowing that we can now stay in 1 bedroom villas vs. the typical hotel room and over the course of the next 10 years of so, pay less for that pleasure.
If you know that you will be going to Disney on a regular basis, enjoy staying in the deluxe resorts, and can book your trips in advance, then DVC might be a great option.
I would say that the only drawback to the program, if you can call it that, is that it does require planning and it is not as flexible in terms of getting your reservations for last minute trips as you can by calling DRC. For us, we always go in the summer (I teach) so making plans 11 months out is easy.
I would say to consider your home resort as well. If you have a preference of where you want to stay, buy there. While you can trade out at 7 months to other resorts, you wnat to be sure that if you can't get what you want, you will be okay staying at your home resort. Of course, if you can't book prior to the 7 month mark anyway, then home resort matters a lot less.
And, check out the resale market as you can get the older resorts for a lot less than you can through Disney.
Good luck!