Clam shell devices are not that comfortable I agree, but I honestly think they could've done better than make a device that is mostly square, and I don't understand why it's so much thicker on one end.
This might sell to people who complained the 3DS screen looked worse with 3D off. And maybe to stupid parents who don't realize you can disable the 3D effect with parental controls, but that's pretty much it.
I don't believe the whole thing about it being harmful to kids either. That hasn't been proven yet. It's just an assumption.
I have read positive impressions of the ergonomics of this from people who have had the device in their hands. No way to really tell until you get your hands on one...it is inherently confusing to understand from people used to holding the clamshell.
I don't believe the 3D is harmful to kids either, but it is an unknown and the whispers are out there.
As far who it will sell to you are missing the point...it will sell to people who think the 3DS has been too expensive. Nintendo has a great library of 3DS games and game that is huge with kids coming out. The last big pokemon came out on DS instead of 3DS didn't it? Why, because DS install base was enormous comparatively. When kids ask their parents for the new pokemon game they are much more likely to get their parents to buy them a 2DS to play it rather than convincing them to get a 3DS.
I only have one 3ds (an XL) in my family and this model may convince me too add at least another one. (I bought 3 DS lites and a DSiXL all brand new back in the day)