I asked the Apple employee here in Tacoma, WA that same question. He said it in quick, I've answered this question a million times today, tone that people start at 4am. So who know if he was serious or just fed up with answering the same question all day.
When I was there yesterday at noon, there was about 20 people in line. The Apple employee said that they were all walk-ins, no reservation, and they would all get a 6, no pluses in stock. If they have pluses, they're gone first thing in the morning. I'm considering lining up myself, but I don't know if I can take lining up again and ending up empty handed again. I might end up "settling" for a 6 out of frustration. My wife said she doesn't want to hear me bitch for 2 years that I should have gotten the plus.