We have one at the St Regis Aspen and it works well for us. It's managed under Vistana. If simply a review of the experience at the property and interacting with Vistana, the experience is good. The staffs do a great job of being professional and trying to take care of us.

Normally I think timeshares/fractionals are a terrible deal, but this one does work for us. They keys are (1) we have fixed weeks at times we want to travel (February and March for ski season) so are not subject to trying to get time that works for us. (2) We purchased on the resale market when it was sluggish and paid 70% less than the original owner paid from the builder. And (3) even allocating an 8% lost rate of return on our purchase amount, with the annual fees we're averaging under $900 per night for a 2-3 bedroom condo in the center of Aspen including peak ski season. I know of nothing anywhere close price wise that's comparable.

Now would I buy a timeshare in Cabo? No way. You can jump on Redweek and grab weeks at nice places (Grand Solmar for example) at less than the cost of the annual dues the owners are paying. And there's about a hundred options.