Just did it this afternoon-
2:46PM EST, logged on
2:48PM received a message from CM saying she was with another guest and would be with me next; asked for
DAS guest's name, first day in parks, and names of people in our travel party.
3:01PM she asked if DAS guest was with me
3:02PM asked me to "reaccept terms and conditions" (she sent a link, even though I had already reaccepted them just prior to chat).
3:04PM she asked if it was ok to have a video chat
3:06PM we were on the video chat,
3:16PM EST we were completely done (CM took care of our DAS advance selections on the call)
I had a lot of anxiety about this since we had only ever registered in person at Guest Services in the parks before - we are going next week and surprisingly only two of the DAS advance selections were fully booked (one of which was for Test Track which we wouldn't be going on anyway). We just assumed we wouldn't get Advance Selections for this trip so that was just a bonus.
Edited to add: exactly 30 days from today is Thanksgiving Day; presumably a lot of people aren't having their first park day/arriving exactly ON Thanksgiving (or if they are maybe they signed in first thing this morning) so I feel like we got really lucky with the online registration time today.