I won't be there (waiting for 3G). The system for the 3GS launch, and I'm sure it will be the same for iPad, was two lines starting at the door and winding around the corner of the building. One for pre-orders and one for people just showing up. They use barriers to separate and guide the lines, and employees are all around so no danger of cutting in line. They only let a few people into the store at a time to pick up their stuff.