I think every BB is handling it different.
I got a call from BB 6 hours ago telling me that they're not doing appointments anymore because they got SO many more pre-orders than they anticipated, so they're going to be well stocked. They told me that every person that pre-ordered will be guaranteed a phone and that all the pre-order customers could go pick it up anytime from Friday-Sunday. They went on to tell me that they'll be opening early on Friday, so I plan on being their early before work, so that I can just pick it up and get to work (relatively) on time.
I asked them if I could personally set up an appointment, due to my schedule, but assured me that there would be no need to and pre-orders would not have any issues getting in and out with their EVO upgrades.