Okay... so I have to ask the obvious.... why would you NOT Pre-order online....?
If you can pre-purchase ahead of time, from the comfort of your house and have a guaranteed phone and probably receive it on or near the release date... is there a downside...?
I don't know if it's always true... but if you order online, and there's an issue, you have to deal with exchanges, repairs, etc. online. With some stores, if you buy in the store and there's a problem, they'll make the exchange or deal with it right there, and may or may not deal with an online bought phone.
Just something to consider.