I think the answer of "value" differs with different people, situations and "when" originally bought.
Thankfully we had the resources to buy two units (Myrtle Beach and eventually Lakeshore Reserve Deluxe) before the points system debuted. At work, everyone considers me "cheap." I prefer to call myself "thrifty." We are not known for wasting money.
In the first few years, we traded Myrtle Beach every year and got fantastic trades and bonus weeks from interval with few restrictions. So we essentially got two weeks for the price of one for many years. Later we added Lakeshore (I swore I would never buy a timeshare in Orlando) because the deluxe model trades as two one bedrooms (not a one bedroom and a studio). That scheme worked wonderfully for a long time-- our one bedrooms were easily pulling two bedrooms in two bedroom only resorts.
As we all know, the game is always changing. The interval bonus weeks have become basically worthless to us. The one bedrooms from Lakeshore are not pulling nearly as much and Interval has added an "upgrade" fee even when I'm downgrading season on the demand scale.
I've converted to points a few times -- giving me flexibility to add nights to "WEEK" vacations or to allow for short stays.
I would say without blinking an eye that our timeshares have been worth it for us. We were fortunate enough to buy when our children were very small. The truth is we have stayed at much nicer places than we would have been willing to pay cash for over the years. We have enjoyed, and been spoiled by, the extra space and kitchens (even if you only do breakfast and snacks-- a major reduction of hassle and expense). The timeshares have encouraged us to visit places we probably would not have gone to (France, Scotland, etc). We never would have gone to Atlantic City for a week and explored Cape May and the New Jersey coast if we had not traded into the Marriott there. We probably would have visited San Antonio for a few nights, but a full week there allowed us to explore other outlying areas! All of this adds up to the vacation "opportunity cost" when doing a full analysis.
Generally speaking, I think timeshares "can" be worth it if one is committed to learning the system (otherwise they are the ripoffs we've heard others talk about).
I do think buying in now for the first time with Marriott points makes the economics more difficult. I'm not sure I would encourage a friend to buy from scratch now. I can see supplementing weeks with points under some situations in order to use (but not for the reasons of inheritance or gaining Marriott status (which is changing!).
Looking at the money is important, but "some" flexibility, usage, frequency is hard to pin down to an exact figure.