I have to admit, I was really hyped by the switch reveal. I think it will be really successful at launch and immediately following. However, upon review, I think sales will ultimately slow and it will fail in the long run. All the functions and different ways of playing seem impressive, however, none of them seem great. Here are my thoughts, let me know if anyone disagrees.
1. Portable. This device seems bulky for a purely moblie device. Can't be popped in a pocket, and battery life is probably not great. I'd rate it as a mediocre mobile gaming option. The 3ds is much better.
2. Portable screen with joy-con controllers. Let's be real here, nobody is going to want to cramp around a 5-8 inch screen with a friend. This is not a realistic way to play. Also, either the joystick or face buttons will be centered rather on than at the edge. This is made worse by how small the joy-cons are. This is a non starter.
3. Home console. This is what it was made for and my biggest concern. The device will almost certainly be underpowered compared to Xbox or PS4. Especially with the almost certainly lower compacity internal storage and cartridge relative to blue ray. This despite the fact that there is nothing unique that we have seen about playing this way like the Wii or Wii U had. So as a console it will be inferior to the competition.
For a multi function device to be successful, it has to do one thing really great. Think the original iPhone. It was mediocre phone, and an oversized iPod, but it was the greatest mobile internet device anyone had ever seen. The Nintendo Switch so far does not seem to do any one thing greater than the competition.
1. Portable. Is 3DS a better portable? 3DS launched with battery life of 3~5hrs where 5 was maximum with no 3D and low light settings. NS is rumored to be 3hrs. To me that is not much difference, especially when DS had something like a forever battery. Being able to fold the 3DS and put in your pocket/bag was definitely a win. But this is a 6" screen with what looks like another inch or so of a frame. I have a 7" tablet and it fits in my back pocket just fine. Many people carry tablets of this size or larger without issue. I think mass consumers don't really care that much, but yes 3DS was easier in this regard.
Minor advantage to 3DS but, NS is still a decent portable device. Which sold better in later years 3DS or 3DS XL?
2. Joy-con. Its so hard to state how these will feel in your hand based on that video. Connected to device, I think this looks great and likely more comfortable that gamepad. Disconnected, I'm unsure if I'll like. But if its similar to using Wiimotes, then it will likey be fine. The nunchuk was perfectly comfortable too, so I have faith this will be fine. As for local multiplayer on 6" screen, I don't think that is a big selling point either. But I don't think it makes or breaks the joy-con setup nor is it the main purpose of this form.
3. Home console. What you really mean here is raw power. From NES to Wii generations, the most powerful console never was the most popular with consumers. This gen is the first time best raw power is leading the generation. This arguement is rather silly as in all reality it comes down to the software, even in this gen with PS4. PS4 has all the same games as XboxOne and it launched at what was basically a better price point with no negative buzz. The power was not the core reason PS4 is winning in sales at all. Just like raw power wasn't why Wii decemated its competition and only went on decline once software dried up.
NS can do fine so long as it has exciting and unique software, plus the major 3rd party titles, which lets face it go on every console they can. You wouldn't see that list of partners including heavy game pushers like Bethesda if the companies didn't feel they could put content on the device.
Also, I think you don't understand how carts work for games. They are significantly better. Data transfer speeds are faster, they can hold far more data at marginally increased cost and they could be rewritten on if desired (updates). Though you are right that the default internal storage will be less as Nintendo will stick with flash memory (which is better than a HDD) and allow SD Cards/ext HDD as people want.
Really the verdict on this will need to wait until Jan/Feb when Nintendo and others start showing off their game support in 2017. I think the evidence is there to suggest that the games will be there to make this a very viable product even when PS4Pro and Xbox Scorpio launch. Plus, Nintendo is now clearly similar to architectural design as the mobile world and can continue to launch a new revision of NS every few years, just like MSony are doing, at the similar pricing to keep up with MSony's own revisions.
As for your final point, all I have to say is Nintendo IPs have by far the biggest value there is in gaming. Main line Mario, Zelda and Pokemon on the same console? Check and mate. Don't forget Nintendo's push into mobile, I wonder why this has a tablet multi-touch screen as well?