After carefully looking at it, the consolewith the tablet in looks to be about the size of the Wii U. However there looks to be about an inch or so tbat is not the tablet. When it was pulled out, he put the detachable controllers on. There is clearly at least an inch below the buttons if not a bit more. 

I honestly though it waa at least 6.5 to 7 inches. I remember rumors saying 6 inch but it looks bigger. What do you think?

I thought it looked smaller than the WiiU gamepad...

seems like 20-25 cm in the base and 15 cm in height.About that

It's not very big, but there has to be that balance

Since you can leave the switch controllers attached to the screen and play it like a PSP, it has to be small enough to do that as well, but big enough to play it as a separate screen, which I don't think I would be using since it would be too small to see :/

ipad Mini size maybe?

In the 6-6.5in range. It's got a decent sized bezel, which made it look like 7in. At first, but watching it again it can't be that big. That bezel makes me think that they expect users to have reason to hold this like a touch-only tablet. I can't wait to see what other kinds of software support this thing will have. Hopefully they plan on releasing tidbits of information regularly from now until march. That'd explain the late reveal, at least.