I'm a AAA dev who works with an actual NX devkit. I've been developing a game for it for about six months.
I will not post pictures, and I won't tell you where I work because I don't want to risk losing my job. However, I can tell you some info on it without giving away to Nintendo or my boss who I am.
For starters, that "leaked" NX controller is a fake. It's really convincing, but the controller that we have on our devkit is nothing like that.
Our devkit's controller:
Doesn't have an oval screen. Ours is a standard rectangle.
Has physical buttons with a screen behind them. It doesn't have a form shifting screen, nor does it have a touchscreen with haptic feedback.
Is hardwired to the devkit, which looks like a boring black box with some USB ports and a disc drive.
However, that fake does get a couple things right. It does have scroll wheel shoulder buttons, but in addition to them it also has two regular shoulder buttons labeled ZL and ZR. It also has a headphone jack in the bottom of the controller.
Some other things I can tell you:
I don't know if the NX is backwards compatible with the Wii U or 3DS or not, but it doesn't look like it is. The system is different enough from both that I think it would be hard to play games from other consoles.
The controller is sort of a game system in its own, but it's not a replacement for the 3DS. It works like a companion app on a phone, and you can take it with you and control some things from your game, like how the VMU on the Dreamcast let you take a Chao with you and train it.
No one outside Nintendo knows what the NX's name is. It's still the NX here internally.
Ask me anything about the NX devkit, and I'll answer as best as I can without revealing who I am.
No way of verifying it of course