The absolute best thing about this system is that a new vehicle arrives every x seconds and there is no bus, boat, or monorail that can compete with that. There is no way for the sceptics to argue with that fact. The lower cost and fun factor are nothing but a bonus.
And frankly to the A/C crowd: you're walking around in the open FL air all day, 10 minutes more isn't going to kill you. You go on the railroad, you go on the caroussel, you go on the tea cups, you ride Dumbo, you drive the speedway cars, you sit in a Splash Mountain boat, you go on BTM, all outside without A/C. Or do you go around the parks in an air conditioned clone of the Pope Mobile?
Why is it not an issue on those rides? Relative velocity, my friend. If you are moving you will feel air moving towards you at the same speed in the opposite direction. Aka a breeze. And before someone brings up that you're not moving if you're stuck, so there won't be a breeze... if the system's down there won't be A/C, either.
And specifically to he who does not trust any tests during which he was not present: you're gonna be bored out of your mind at WDW because you can't ride any of the rides that were tested without you. How do you know they're safe?!