Around 9 there were a lot of people talking about going and a lot of people talking about all the traffic outside Disneyland and the line heading in, but they were still letting people in. So i decided i should wait a bit and see if the crowds had peaked or not. Then between 9:30 and 10 the official Disneyland twitter announced they were at capacity. Other people said they were still letting people in at a trickle as other people left, but obviously with a huge line waiting that isn't much of a help. So i just checked back every hour or so. Around 10 there was another official tweet saying they were still full. I finally crashed shortly after midnight, though i'd pretty much given up on the idea well before that. Between not having anyone to go with, lots of traffic, a long line, and no actual guarantee of getting in, it didn't seem like the best use of my time.
Apparently around 2am enough people had left that they officially opened the gates again. So if i'd been willing to stay up and head out at 2 i could have had a good three hours at the park =P
So clearly if they ever do this again you need to get there relatively early in the day if you want to be sure you get in, or go with a bunch of friends who you don't mind hanging out with in line for a few hours. (Or even better of course, both =)