The Switch will be my first "at launch" Nintendo console ever, with my other launch buy-ins being the PS4 and the Vita.
In all cases, there was something exciting about the hardware that caused me to need it day one:
with PS4, it was built-up fatigue over the length of the PS360 generation. With the PSV, it was the promise of "console gaming" on the go (a promise that was generally left unfulfilled, although I'm more than content with the niche gaming monster we ended up getting).
With the Switch, I feel Nintendo has a shot at achieving what Sony attempted twice but didn't quite hit - the console experience, made portable. Portability can do a lot to make up for a huge power gap, at least in my use case (ex. buying World of Final Fantasy and Digimon for Vita instead of PS4, despite having both), and if we get the 3DS-style library of quirky, portable-oriented games as well, the system has a good shot of carving out a niche.