I've stayed in many in Miami (Condrad, Viceroy, Fountainbleau) and have done some investigation as to the viability of them as an investment. Generally, while tempting they are not good investments now.
You would think it was a good deal... Own a condo that you can use as a vacation spot or permanent home and when you are away you enroll in the accompanying hotel program. The only problem is the maintenance fees are generally much higher than other condos (because you have hotel like amenities) and rule for the hotel programs are usually very restrictive (you get filled last, they take a large %, you have to enroll a certain % of the year etc).
In times where real estate isn't appreciating AND people are not staying in hotels they can be really losing investments... in good times who knows.
What is much better is to just buy a condo or property and rent it online on your own via homeaway.com, vrbo, or airbnb. You get all the benefits of a condotell and you save the middle man and cost that goes along with it. Of course if you are planning on traveling far away where you can't service your property a condotell might be better.