Definitely bring your ID. We just got back from using ours, and the day we activated them, the ticket machines at Epcot (and I think at all the parks) went down. The lines were really backed up, so I went up to use mine for the first time, and the lady was trying to hurry people through, so she didn't have me put my fingers in for the biometric scan - she just hit a button and waved me in. Well, that was fine and good, but then I had problems at every gate. I had to show ID twice, and they said they were resetting my biometrics, but not until our last park of the last day did it work. What a pain. So bring your ID with you at all times for sure!