I want it day one and managed to successfully get a preorder through with Best Buy a few hours after the presentation (we'll see how long that holds up).
I've honestly been saving cash since we got the Switch reveal, and thanks to Christmas money, I've got enough for the system. I want the game that will hopefully reignite my passion for Zelda to be the best it can be, and that trailer we just got convinced me that the series is finally moving forward in a good way.
Zelda is enough of a reason for me to buy day one, but it's also the fact that Nintendo loves its artificial scarcity. If they can't keep up with plastic toys and a glorified emulator, I doubt they'll keep up with a $300 system. In the event that we do get more launch games that interest me, I don't want to be caught being unable to get my hands on a Switch.
Plus I'm going to get one anyway. I'm still a Nintendo fan, and since I already have the money, I don't see an incredibly compelling reason to wait.