How does it work? I've never heard of fueling without the cap. Is the door the new cap?
It's probably hard to imagine and you'll have to see it to understand. But it works fine.
It's nice not having to fumble with a gas cap or run the risk of it falling on its tether against your paint.
(1)You can't stand there and wait for it to fill all the way up, then top it up some more, and then yank the nozzle out. That's going to make for trouble. The days of topping up are gone. You have to just let the nozzle turn it off, and then take your time (like 15s) to take the nozzle out in order to be sure that the capless system has trapped everything.
(2)If you run the car out of fuel, this is problematic. There's an insert in the trunk (under the floor) that you have to remove and use in the filler if you're having to put fuel in from a can.
But I have to say, the system is working fine for me. No troubles whatsoever.