I mistakenly "reserved" 2 phones online to be picked up at the local store. I stopped by yesterday and spoke with a person at the apple store, and she just went into the screen that showed all the reservations (~700+ as of noon sat.) She did a quick spotlight search for my name and it showed 2 reservations, so she just cancelled 1.
I specifically asked if I came at 7pm after work, if I would have one available. She said she didnt know how many the store was getting, but they would put aside the reserved ones as they did with the 1st iphone. I do recall that I came pretty late in the day when the 1st ones went on sale, and I had no issues getting one. But then again, the store here is no where near as crowded as some other markets.