First, there were women. I don’t know the percentages, but after going to a handful of Microsoft-sponsored developer events that have very high percentages of men, the women factor caught my attention.
Now, SIGGRAPH isn’t exactly a developer event, although there were a handful of us around. I’m guessing that the majority of the attendees were content creators/artists and the remaining people were from academia. I’m guessing also that the majority of the women came from the latter two groups.