It will be interesting to see if this is intended to replace the 3DS. It seems like they are going that way. I think I'm fine with that as long as it retains some of the features that made the DS/3DS such great systems. It doesn't have a dual screen, but I'm not very bothered by that since the second screen has been mainly used as an immediate pause menu or minimap which could easily be done on Switch games using intuitive touch controls.

Another feature it needs is the ability to suspend games in a sleep mode to preserve battery and prevent you from having to boot everything up each time you want to play. This is standard these days but I mention it because WiiU absurdly doesn't have this feature.

The other issue is the games. Obviously any system will be rated based on its games but in particular Switch needs to continue the legacy of great portable games that Nintendo has consistently held up over the years if it is going to replace its latest successful portable system. Series like Fire Emblem, Professor Layton, Pokemon, various Square-Enix ports and handheld titles, and the Zelda handheld series need to be able to continue to thrive on Switch as true next iterations of those series. For that to happen Switch needs to prove itself as the next generation of handheld gaming and not just the next generation of console/handheld hybrid gaming.