when i saw the keynote in 2005 (i didn't have to stand in line to see it in 2006 - that was a nice change), i got in line around 6:30 am. the line starts forming *outside* and by the time i got there, the line was already winding around the corner of the building. they did open the doors of the moscone center fairly early (don't remember the exact time, but it was still dark out) and allowed the line to snake around inside.
the doors to actually get into the hall where the keynote is held opened just about 10 minutes before it was scheduled to start, and it was a madhouse! all of the fabulous seats up front are reserved for the media and VIPs. i was by myself and ended up chatting to the person next to me in line and we worked out a little tag team plan beforehand - he found a pair of seats for us right away and held them while i scouted up closer to the stage for better seats. once i found some, i called him over and he relinquished the first pair of seats he'd found. definitely beats rushing around trying to find the best seats possible and then finding nothing in the madness and ending up sitting on the floor...