While I agree the online reservation is easy. I had a bad experience overall. First, it's easiest to pay with a swiped credit card rather than entering all information online. Then the shuttle schedules you way too early for your ride. In my experience in Pittsburgh, the shuttle came almost 20 minutes early. I received a 4:47 am call say, "your supershuttle ride will be there in ten minutes. Out of courtesy to other passengers, please be ready." my scheduled time for pick up was 6:15-6:30! What was most obnoxious was no other rider was waiting!
Then it was pouring, and the driver wouldn't even get out of his car to open my door or help with my bag.
Then we ended up waiting almost 15 minutes picking up the next passenger, because we were so early!!!!
Would not recommend! Take a cab!