The important thing to remember is: there is no such thing as one answer when it comes to timeshare. For example, while some folks report very poor experiences with Weeks, others will report very good results. That's to be expected, because any two timeshare weeks are likely to be very very different.
Some timeshare weeks are effectively worse than worthless---they are worth less than their annual fees. For the worst of the worst, you can't even give them away to the several charitable organizations that resell unwanted weeks on ebay and other auction sites. Prime examples include off-season weeks, in small units at no-name resorts in highly seasonal destinations.
Other timeshare weeks are very expensive---both to buy and own---but provide decent value. DVC is one example, as are some of the Marriott, HGVC, and Starwood properties. Even here, you have to be careful.
Every once in a while, though, you find a true diamond in the rough. A week that is inexpensive to buy, inexpensive to own, but happens to have high demand relative to the availalbe supply. It takes a lot of time to learn what such a week might look like---it's not immediately obvious. But, if you find one, they're great.
For example, I own a week that I purchased for $275 (including closing costs and resort transfer fees). The annual dues on this week are a bit under $500. This week turns out to be a great asset. When I deposit it with Interval, I can get two DVC weeks in exchange. In RCI, it gets the hardest-to-get trades, including New York City, San Francisco, Southern California coastal, etc.
Of course, the value of that week could disappear tomorrow---either because the resort board allows unit quality to falter, or another developer builds a large resort nearby, etc. So, it could all disappear tomorrow. But, becuase I have very little invested, that would be okay.
If this is something you are interested in, TAKE YOUR TIME. It is very easy to buy a timeshare, but very hard to sell one.
