We used to Park at Pre Flight parking. Nothing was "wrong" with them but we decided to try this place as it was closer to home. We were immediately impressed with their service so we decided to try them again. They have continued to impress. They also do contests on Facebook from time to time for free parking which that helps.
We travel quite frequently and have gotten to know a good amount of the drivers and the cashiers. Everyone has gone above and beyond their job. We once left a cell phone on the shuttle and when we got home and realized what we did, one phone call and they had the cell phone waiting for us. They even tried to refuse the tip we tried to give them.
My only suggestion would be in the summer time to have cold water bottles for their customers as they get back to their cars. Pre flight did this and it was a nice touch. Blue Sky DOES usually give out free cookie coupons and this is a HUGE plus as well.