So, i've waited a little to give my feeling about it. As usual it will more be about the way i think it could work or not, than my personal needs and enthusiasm about it. Also it will be cold hearted.
What could make it a success:
_The fact that it's a really capable portable, like never before, and it'll have amazing Nintendo games on it with full production value
_The fact that it allows for never seen before local multi for many games, Splatoon, MK and i hope way more? That's the real strengh here, nothing else. That's local play by LAN that allowed Monster Hunter to sell 4 millions in Japan. Same for Pokemon Go. Build a strong community of player that can play locally together.
The weakness is obviously the whole detachable controller that seems to seduce nobody (not the one with a hub but the half ones). THAT right there is that little thing Nintendo always does. Designing the whole console, restraining it around one single thing that you absolutely want but nobody will really like it. Like the 3D in the 3DS, like the of tv play on WiiU. Actually my bad, 3D and off tv play are awesome, BUT they never sold the console enough to justify the concessions they needed. This time, it seems even worse when you think about it. I mean the idea to be able to play on the go with one console is cool, potentially.. But will it take on ? Will the console be well designed for kids to use that feature ? Will gamers accept to play with those horrible mini pads ? Will casual gamers care? WIll the cost of the console even allows it to touch occasional gamers ? This is really uncharted territory here. I could see it being a good idea that never worked in reality.. and never touched his audience.
The other big weakness is how they are basically telling everyone "This is a WiiU". They show us 3 games that are on WiiU, with the same visuals, + a Mario game that seemingly could run on WiiU without any problem. That's the reveal of the machine. So they are absolutely assuming the portable WiiU aspect. Except if they market it as a portable, as a new 3ds, that's fine. But as a "home console" as they said, it's going to be bloodbath. I mean Nintendo fans will buy it but guys but others.. (i just had a friend on the phone who is an ex nintendo fans, you know the usual "i regret the Nintendo of the 90's", and he was pretty violent with it. basically saying "i don't give a shit and Nintendo is dead to me." i'm telling you that cause we don't always see how guys outside that circle see things)
Let's say one part of the job with that new console was to cut any bad WiiU connection for people. Well this is TERRIBLE from that pov! The worse they could have done.
An other unknown data, and a BIG risk for Nintendo. Take the console as a japanese successor to the 3ds and NS. I mean, look at the NDS, then the 3DS, who was already less appealing and more gamy, then look at that. I really don't know how the japanese market will receive it, as a stand alone portable. The whole Local play could be HUGE there but the design hmm, who knows... Never forget the NDS became a phenomenon on Japan only after the Lite redesign. Cosmetics count.
Anyway i'll stop there but in a sense, what i'm saying is, in my opinion this thing can find a way to a success, probably more than the WiiU in its time, cause the concept is just more modern and unique, but it also have all the little seeds for absolute failure. This is a risky move for Nintendo.