I don't know if taken your trip already but I frequently take Yellow Shuttle (next to SUperShuttle) and they are $1 cheaper and have a regular circuit to Fort Worth (stopping at the major hotels). You may wait in the airport for about 15 minutes for other passengers but it is pretty direct (roughly 20-25 minutes from airport to hotel). This is during business hours (for almost the past 3 months) so can't speak to off-hours service.

I took SuperShuttle once and it was a tour of two towns prior to Ft. Worth.

In reverse - you can typically stand at the Sheraton or Hilton and get into an unreserved shuttle within 30 minutes from either company as I believe SuperShuttle has the early AM until 1pm and Yellow Taxi has the routes/pickup until later in the evening. This works out pretty well assuming you allow 2 hrs before your flight don't worry about scheduling.