An average store will maybe have 20-30 people waiting out front (and mostly for that "free gift" which is probably like a $20 itunes card) when the store opens, and out of those people, probably only 5 didnt reserve.
Several weeks ago there was an article saying they were an average of 700 reservations per store. Do you really think less than 5% of those people will be picking up their iPads?
I'm 100% certain the lines at every store will be long enough to make the local news.