very easy to use
The driver was the best one we had in our 2 weeks in Europe. He was easy to find, spoke great English, offered us some of his own money to use the restroom, looked up our flight to determine the correct terminal to take us to and told us how to properly navigate the Madrid airport.
They contract out to local cab companies. They take their fee and take no responsibility at all for no-shows. I will never use their service again and will urge others not to risk it.
The driver never showed up and Shuttledirect accepted the driver's version that we never showed up despite the fact that we presented evidence to the contrary (including phone records showing that we tried calling the local company... we were answered twice by a non-English speaker who just put the phone down on us).