I had originally booked my shuttle through airportexpress.com and Showtime Tours was sub-contracted.  When I arrived at the airport they told me I had no reservation.  On the phone for an hour, they finally found my reservation.  On the way back to the airport, the shuttle never came.  I called again and was told I had no reservation.  Whatever, it was $12 - I just took a cab so I wouldn't miss my flight.  At first I thought the problem was with the website I booked it on.  Nope, I've since used Showtime Tours twice and have had problems every time.  I will NOT be using this shuttle service again.