I'll chime in with my "how I decided it's worth it"... and I'm going to round / estimate / guess, because I don't have my exact #s handy.
I have 2 trips planned at 11 months apart and I figured (best case scenario - if I wasn't even considering DVC) I'd be booking 2 rooms at POR with Free Dining and tix at a cost of $10,000.
I can buy 60 points direct at OKW, use the current AP promo and pay oop for only the food we eat (not the excess we get with free dining) at a cost of about $13,000.
So, assuming some future non DVC 3rd trip several years from now would cost me over $5K, even with a new set of tickets and annual dues, I'm close to breaking even on trip #3. After that, it's costing me annual dues for my room.
Since this is spending a relatively small amount of money and I can still break it up / spread it out a bit, I'm not even going to try to calculate interest I'm losing, etc and so on. I was spending $10K over the next 2 years no matter what and it's not coming out of an investment fund, it's coming out of my checking account and a little savings.
Done. I'm in.
Truth be told, I've been holding out in case the perfect resale came along. Then I'd likely be buying 75 points (50 resale, 25 direct), not 60 and all my numbers would change (but I'd have a little more wiggle room with points) and I'd buy at BWV instead of OKW. Even if I buy BWV direct, I think I will about break even in 4 trips, so I'm still good with that. Then I was looking at Copper Creek...... lol. You get the idea. I'm going to have to pull the trigger soon! Decisions, decisions....