Just back from out first POR stay!
I did the Online check in thing. I must say it is a bit of a confusing concept at the POR.
When you arrive at POR you have to get on the same line as regular Checkin. Sort of defeats the purpose. However there is a seperate window for Online checkin. It is all the way in the back of the Hall.
However when the On Line Check In Window is empty, they didnt call "Next". (this happened to me & someone else I was talking too at the POR). You pretty much have to pass everyone in line ("Excuse me", Excuse me

and hopefully none of them are waiting for Online check In window, and not paying attention.
The setup is problematic, so be aware.
Anyhooooooo Once I got to the window they verified my CC info I gave online. Handed me a map to the area our room will be "most likely in". (the room wasnt ready yet). Got our cards and went off to the parks.
Not any great time savings, and certainly not useful if you want a "better room". We were all the way in the back in Section 35 Alligator Bayou. I had a car, so it was no big deal.