I had a super positive experience with the round trip Bell Trans airport shuttle. When my boyfriend and I arrived at the airport in Vegas, we headed to the shuttles area and thought the $14.50 round trip per person cost was pretty good. We didn't have to wait any more than 15 minutes to depart and were dropped off right at our hotel on the strip.
I called the day before to schedule a pick up for 12:30, and the driver promptly showed up at 12:25 and took us straight to the airport. Depending on who else schedules the shuttle, you'll most likely make multiple stops at other hotels before going to the airport.
Wonderful experience. Very fast service, and I was glad I could rely on Bell Trans to get my boyfriend and me safely to and from the airport in a timely matter.