I wanted to see it the first night (the day after Thanksgiving) and was unable to get a dining package reservation, so I thought I'd wait in the stand by line. HAHAHAHAHAHA!!!! By 4 pm (for the 5:00 show), the stand-by line was so long it was being roped off into several back and forth weaves past the boat dock at Italy. Many of the people standing in line DID get in -- they do seem to leave quite a few seats for stand-bys -- but you REALLY will need to get in line quite early for it. I'd suggest at least 3:30 pm for the 5:00 show on Christmas Eve -- I imagine that in the next couple of weeks it will be very easy to get in on standby, but not on the first day or Christmas! I was trying to "mark" the crowd to see how far back the last person let in was standing, but I lost track (trying to keep two kids occupied . . .just didn't work!)
Now, on the plus side, I was able to see part of it from the walkway in front of the pavilion (along with tons of other people -- we didn't get to sit and we didn't have a great view, but it was still lovely despite the aching feet). So you CAN see at least part of it, and it really is lovely.
Good luck!