I'm surprised people have had that long of a ride with SuperShuttle. We've used them almost every trip over the years (so at least 16 times, one way). We've had to drop people off before but it didn't take more than 5-8 extra minutes off the commute to our hotel. The most we've dropped off before us was 2 parties, and that's if we're the last ones off the shuttle. 16 extra minutes to get to the hotel isn't much at all. Most times they group people going to the same area hotels together.
The only problems we've had with SuperShuttle was one time during rush hour when we were going to our hotel, which wasn't the drivers fault. The traffic was a doozie! The other problem was when we were heading back to the airport from our hotel. He showed up around 30 minutes late to pick us up. Kinda frustrating, but we were fine on time because we had a pick up time that was hours before our scheduled flight departure.