the 27 is the offical date that the game goes live and the release date by anet. But they game in some places might be 1-2 days before the 27th. I beleive best buy has the date as the 26th and not the 27th. Your best bet is to call around and ask Or do what i'm doing, i plain to hit stores the 25th and 26th and if no luck, go out the 27th again. But hopefull i can score the game before it hits so i can read all the information that comes with the CE.
If you're worried about playing the game don't worry. Getting the game on the 26 or any date earlier then the 27 it will be nothing more then a CD in a box with some papers. As mentioned before the game goes live on the 27th. If you're going to have a conflict picking it up on the 27th then yes do call around see if someone has it in and if they will sell it.