My family has occasionally done these timeshare presentations, not always at Disney. In fact, we just did one last year at Hyatt Grand Vacation in Bonita Springs, FL. Nice, cheap getaway, and living in FL makes it easy to take advantage of things like this and explore places in this state that we have yet to see.
It is true that there is high pressure. Some sales people are higher pressure than others! And, the resorts and the sales pitch can be very enticing, especially if you are in "vacation frame of mind", having a great time, and you want to do things like vacation again! It can be very hard to stay strong and keep declining the purchase, but it can be done.
There are two ways we go about this, depending on the feel of the moment. Sometimes, just declining, saying, "no", is enough. Other times, we resort to, "I have to go home and speak to my financial advisor first". The salesperson will keep trying, possibly telling you that the offer is only good that very day, but just keep repeating that, don't offer any extra explanation for them to try to work around, and they will back down when they realize you aren't going to purchase that day.
It doesn't matter if you have a financial advisor, or not, the salesperson will never know. But, it gives you a way out if you aren't comfortable with just saying, "no".
We have been to some interesting places with these deals, and some places we did not care for. As long as you remember to keep the upper hand and make sure that YOU are the one in the position to walk away, a timeshare deal can be a less expensive way to experience a vacation destination.