The deal is good, but definitely find out where you'll be staying for that rate. As for the sales presentation. I attended 3 of these with Vistana. The two prior to when Sheraton took over Vistana were pretty low-key, though the sales person was trying to be as enthusiastic as possible. The third (and my last with Sheraton) was VERY aggressive. This was in the summer of 2000. The sales guy did not want to release us after 90 minutes when we informed him we wanted some time to think about it. He dragged out the presentation close to an extra hour and appeared irate that we wouldn't commit right there and then. We literally had to tell him that our time was finished with him and we had satisfied the timeshare presentation. This guy was red in the face with us and quite rude. Two and half hours of wasted vacation time and stress to boot for $50. Even $100 wouldn't make me want to go through that again. On top of the actual sales people at these presentations, I feel that Sheraton Vistana is aggressive with trying to get you to attend these presentations or sales breakfasts when you stay at their resorts. I got at least 4 phone calls during the course of a week this past August direct in our villa. They didn't seem to want to take "no" for an answer when I told them we did not want to attend the "breakfast". Next year I plan to unplug the phone when we check into our villa.
Good luck in your decision. I, personally, would not do it unless 1) I was very interested in purchasing or 2) I was on a very tight budget.