I think I've been to 3 presentations over the years. One in Vermont was for free ski resort lift tickets, one in Orlando was for free Disney tickets, and one in Whistler, BC, was for a free dinner. Damn near bit on the one in Vermont, but I was young and stupid back them. The one in Orlando was the most entertaining. We knew what was going to happen, so we just sat back and "played" them as each manager came out and tried to convince us to buy, until they got downright rude and called us all kinds of names because we were turning down such an unbelievably "awesome" opportunity. "Gosh, sir, we were almost ready to buy on the spot until we heard there were alligators in your lake."
Fortunately, we got our Disney tickets without much hassle, so it was worth our time. The Whistler one pissed me off because we were very clear that we had children when they signed us up for the tour, and then at the end they said there were no children allowed. So when my wife got indignant and walked out, that apparently negated our right to the free dinner coupon. Never again.
My brother has a time share in Orlando, but to my knowledge he never uses it. Rentals pay for his maintenance fee, but that's about it. On the other hand, I have a sister in Scotland who had great luck, getting in early on the first timeshare development in the Highlands, which actually appreciated in value. She was able to trade up, and actually ended up with timeshares in both Scotland and Spain as part of the bargain--and she still uses them both.