I got on the 8:50am train yesterday which arrives at GCT at 10:15. The train broke a bit and I got there, 10:30. No big deal. The con opened at 11. I walked over. Stopping at Staples and Book Off on the way.
I got there around 10:50pm, not bad at all. There was a nice sized line for on-site reg, but not even close to Otakon sized. I expected a 30 minute wait. After about 15 minutes a guy with a megaphone said "sorry, the fire marshal said we're full. Nobody else is getting in". I heard that at 12pm even if you pre-registered they turned you away.
Maybe this is why nerdy conventions in New York are never succesful? More on this on GeekNights this week.