I was also firmly in the on-site camp, but we planned a last-minute trip (after not going for a few years)last fall,and I couldn't hack the Dis prices. We bought a week at a Calif. timeshare two years ago, and my eyes have been opened to the timeshare deals.
So, we stayed at WBC last year and loved it, esp the space. There are timeshare resale agencies you can use. Call Wholesale HOliday Rentals, that's who I used and they were great. Vacation Upgrades is another. You can also check ebay. Remember, prices are lower within 60 days of travel, so if you can wait, that's a great way to go.