0:26 I see two USB ports on the front, not much else. Probably more at the back, plus other connections.
0:30 The controller layout looks pretty basic. It... has four direction buttons on the left rather than a standard d-pad. I dunno how I feel about that. It also looks in other shots like there's a tiny d-pad in the top right but that might just be a connector of some sort, or the + button. Right side has the analog stick at the bottom, which... ehh, I guess that's more 'normal' by PS/XB standards but I'm used to Wii U layout now. Maybe this is a sign they're going for familiarity for fans of other consoles and thus plan to compete with them more directly again? Or maybe just they found it more comfy.
0:40 Okay it's definitely a + and - 'button' at the top. Not sure how big the screen is exactly but I'd say it looks similar to the N3DSXL screen, judging by the guys hands?
0:42 There's at least two shoulder buttons judging by the action on screen and the right finger position. Probably R/ZR/L/ZL again. Also this means the console can probably play Wii U games - it has two screens and all the same buttons. It would require the screen to be a touch screen though, so... maybe this is wishful thinking?
0:48 (and other points) You can see the logo is just the controller's analogue stick layout, actually. So that's something.
0:55 Cards, pretty small, and they go in the screen unit (which connects to the main unit). Not much else to say about that I guess. Maybe they can also go into the main unit as well?
0:59 I see at least one and possible two buttons on the back, so maybe in addition to two shoulder buttons there's a third button on each side? Maybe a more niche button for some special purpose as it looks smaller?
1:08 Okay this bit is pretty awesome. Suddenly it's a tablet screen, and you can use the controller separately. Also this game looks interesting. Like an Elder Scrolls style first person RPG? I'm not really familar with those sort of games though.
1:11 So you can use the two controller bits separately, it looks like. Interesting. That means both are powered. I'm really seeing where this "Switch" name comes from, that's at least three or four different setups we've seen up to this point (TV + controller, handheld, Tablet like screen + controllers, and implicitly Tablet + controller).
1:23 Looks like a fixed controller, so yet another control scheme option. This one has a d-pad, four central buttons (which makes the theory there were extra buttons on the back seem more likely - we have +, - and two mystery ones now).
1:36 This is interesting. We obviously have Mario Kart, but... is it a new one? It looks very similar to MK8 to me.
1:41 It's not MK8, they have multiple items each. So new MK game confirmed? Also yet another way of playing, each player using one half controller - seems generally uncomfortable to me though.
2:03 It looks like this is demonstrating local connected play, which makes sense to have exist. Also shows another new game, a basketball one.
2:13 A new Mario game as well? Controller looks like the normal controller 'dock' one. Seems like this Mario may be similar to 3D World, but it's hard to tell.
2:47 SPLATOON! Except, this isn't Splatoon (Wii U), the stages look different. So Splat2n launch title looks pretty likely.
2:49 A closer look at the fixed controller. It has a home button, so that's one mystery button solved. The other I can't tell.
~3:00 This is really interesting. It's a big tournament game. Does that mean Nintendo's planning to go more competitive and/or support competitive more heavily? Splatoon was a game that had people begging for Nintendo to provide more competitive support after all, and this really seems to suggest that's something Nintendo is answering. I think this is the most unexpected thing in the whole trailer, to be honest, and it's GREAT.