Also it sort of depends on when they show up. It would be really bad if you had a big group of people show up right before they start letting people in. If that same group showed up at midnight, and you had been there for a few hours, maybe not as big of a deal.
I remember the first time we saw an advanced screening, it was The Avengers movie. When we got there we were about 20th in line and were stoked. By the time they let people in, we were probably about 80th. Still got in and got good seats, but we were getting more and more ticked off as all of these people kept showing up right before they opened the doors.