What do you find to be the "pros" of it?
I strongly prefer the timeshare model of vacation lodging to the hotel model. We are a family of four; our eldest will be going to college next year, and we've owned timeshares for almost nine years now. Having two (or more) bedrooms, an equipped kitchen, a washer/dryer, and a nicely furnished living room makes for much more comfortable and pleasant vacations. We don't often cook, but it's nice for assembling breakfast or even having proper dishes off of which to eat pizza delivery. On nearly every vacation we've taken, my wife and I look at each other and say: "Hotel rooms. How do they do it?"
On the other hand, most timeshare resorts don't have daily maid service, lots of on-site restaurants, etc. It's a more do-it-yourself vacation. We like that, but not everyone does. Before we found timesharing, we were the sorts of people who would rent private homes, or maybe stay in a Residence Inn or equivalent.
Are the MFs worth it to you?
We are probably not "saving money" by owning timeshares. For each of our timeshares, our annual fees are probably a shade less than it would cost to rent the same week, but not by a whole lot. We've gotten more than fair value out of them using either internal point systems or third-party exchanges. But, we are also taking more vacations than we otherwise would, because timeshare assets are use-it-or-lose-it. I view this as a benefit, but it's not a financial benefit so much as something that is good for my family's soul. Truth be told, we're now in a position where it is very hard to use them all, because the kids are both in high school with a variety of sports and other activities that limits our potential travel. I suspect this is a short-term problem though, and in the meantime I'm sending other family members on vacations that they would never take themselves.
If you had the opportunity to pull people aside as they walked into their first sales meeting and give them 5 minutes of advice, what would you say to them?
Two things. One: never buy from the developer. We bought all of our timeshares on the resale market, for a dime (or pennies) on the dollar. Two: take your time. It's easy to buy a timeshare, but it can be hard to sell one. Make sure the thing you buy fits your needs. We've been happy with our purchases, but they were not spur-of-the-moment decisions. If I had it to do over again, I might do one or two things differently, but I don't regret any of those purchases.
Presley's recommendations for "months" is about right. Ultimately, timeshare ownership makes the most sense if you view vacation planning as something of a hobby. You also need to have a pretty comfortable cushion of discretionary income, because even if your lodging is cheap, not much else will be while on vacation.