They will let people with reservation cards in first to purchase their device and while those folks are getting started, the staff will hand out menu cards to those in the non-reservation line to select what they would like. My local MS store said they will receive about 100 devices for the general public to purchase (they do A LOT with the gov't and hinted at lots of bulk orders) and will handout somewhere in the neighborhood of 50-75 reservation cards.
Also, if you purchase on launch day at MS store, they usually throw in a bunch of goodies. I know that they are including screen protectors ($30 value) for free and having one of their techs apply it for you. They might also have cases for free and if you take two minutes to learn about their Windows Phones, they will give you a coupon for $25 off of a $75 purchase which can't be used on the Surface but can be used for accessories.
of course they might be disappointed when they try to upsell me a windows phone and I pull out my lumia lol.
I did see an option to set up a "shopping appointment", any reason to think this could be wise to set up for 10am? I don't really want any help lol, I just want a surface pro :) but if it speeds up the process...