I want to ask something. Just how many people actually used the 3D more then 5 times? Me and most of my friends don't, I know that. The 3D was a nice feature and all but I found myself completely forgetting the 3D after a few days with the system. I'm not sure if it's just me, but 3D makes it hard for me to focus on the game, especially if it's filled with fast-paced action.
Also, now that I think about it, Super Mario 3D Land had some sections where it helps if you turn the 3D on.(Pretty much the game where I used it most because of that) But, I don't really think that would be a problem. It was not used that much as far as I know.(I never did 100% on that game but I did beat the main story and some of the bonus worlds and, as far as I can recall, I only had to use it like 2-3 times and it's perfectly doable without the 3D)
Also, I don't see why so many people are hating on the design. I mean...it looks exactly like an open 3DS with the buttons moved up. It's really not so bad people. I've read a hands on that says it's rather comfortable so it won't interfere with gaming or anything.
Also, you can actually close it in a way. There is a slider that simulates the closing of the screen.