I'm really excited about the Switch, too, even though I'm a biased Nintendo fanboy. The Fallon preview was glorious. So many things to like.
My main concern, though, is the mobile use-case for the Switch. Unless they have some innovative and exciting features that we haven't heard about yet (GPS, Android/iOS pairing of some kind, Netflix downloads, SMS capabilities?), it's hard to believe that there's a lot of people like the 20-30 something gamers in the reveal video. Is mobile gaming really that big of a feature for the majority of console gamers?
When most gamers are on an airplane, they're going to play games on their phones. Using precious carry-on space for this tablet--even as thin as it appears to be--is a fairly big ask, again unless it has some features aside from games. There would need to be fairly significant cultural shifts to see gamers in their 20s and 30s pop out a couple of Switches for multiplayer sessions in the park or at a party, but the Wii brought that kind of big cultural impact, so it's possible. I'd love to get a Mario Kart session going in the back of a minivan someday.
If the Switch can do something really innovative with mobile, something with location, or AR-lite (like Pokemon Go), then I can see this thing really taking off. But if it's just that you can pick up and take your console games with you... I don't really see it capturing a lot of iOS/Android market share.
But as for using the Switch to play nintendo exclusives at home, as a Wii U owner, I have no doubt that Splatoon 2, Mario 3D World 2, and Mario Kart 9 will be absolutely amazing. And I've been waiting for Breath of the Wild since its first announced launch date: 2015. So yeah. Can't wait.