I got my DSi at midnight, but my Gamestop isn't doing anything like that.
But I guess that's a good thing because I have work at 8 in the morning, so I would get it, play all night and then not wake up for work.
Edit:
Oh yeah. For Gamestop it depends on the store. I used to go to one in the next town (Like 15 minute drive), but then they built one a few blocks away (Like 2 minute drive). I got my DSi at the further one, and they had a launch event, and will probably have one for the 3DS, but the closer one is smaller and isn't staying open later than usual.