We did it once in Charleston... on our honeymoon, actually.
We were young and short on funds and sitting through a short timeshare presentation (1-1.5 hours, maybe?) earned us a choice of tickets to 3 different activities/attractions of our choosing (we chose a plantation tour, a horse-drawn carriage, and the haunted jail, I think). I don't quite remember the details, but I remember being glad we did it... because none of those were things that we would have spent our own money on and yet they were all really enjoyable.
Now that we have more money and less vacation time, I'm not sure whether we'd do it again... it would depend on what they were offering. It's definitely not something that I would automatically dismiss, though. I'm VERY good at saying no, so no worries that I'll crack under pressure. (My husband, on the other hand, is a completely different story!)