For the Green Lantern panel (which started at 11:45am), I got in line around 5am and here's the scene at that time:
There were about 700 people ahead of me at that time, but nearly tripled as everyone was holding spots for other.
I tried to get back into Hall H for the Thor/Cap panel (6pm) around 4pm, but there was announcement that the Hall was filled to capacity and there was not garauntee that I would get in, so my wife and I got out of line and went to the Attack of the Show panel at the Hilton.
For the Smallvile panel, I got in line 2 hours before hand.