I have two different experiences in Central Florida. There are three Apple stores in the metro area and countless carrier stores.
The first was with the iPhone 4 which, so far has been exactly like the launch of the iPhone 6. First, it's a new form factor. They processed pre-orders in the same way and had record sales before it even launched. One major difference is that there weren't rumors about shortages. Anyway, arrived at my local in-mall Apple store at 10 PM on Thursday night (the night before the launch) to find 30 people already there. Planted my chair and hung out and had a good time with the people around me. By 7:30, (this will sound like an exaggeration) there were several hundred people in line. Thanks to the pre-order pickup line being worked along side the walk-in line, the walk-in line moved unbearably slow once the store opened. I was 32nd in line and finally received my phone at 12:30 PM. By then there were easily (another one that will sound outlandish, but isn't) over a thousand people in line inside the mall. It was unbelievable.
Last year for the 5S, I went to my local AT&T corporate store at 1 AM Thursday night and was the first person there. I felt a little foolish frankly, but planted my chair anyway. At about 3:30 somebody else rolled in and people slowly started to trickle in from there. By 8 AM when the store opened, there were maybe 40 people in line and I was in and out in less than 5 minutes. This wasn't a new form factor and most iPhone users were not eligible for upgrade.
I expect this launch to go similarly to the iPhone 4 launch.