I own a 3DS and I can tell you I rarely play with the 3D on and it's more distracting than interesting. Yes, it's 3D, but it's not GOOD 3D. I mostly play with it off so I see the appeal of this. What I DON'T get is why they made this so poorly designed. It's a solid piece that can no longer fit in a pocket. The 3DS fits comfortably in all my pockets but this looks too large to even get in a pocket.
That aside, I think this is still a viable alternative for users that don't want the 3D. It's cheaper, can play the 3DS and DS games, and still has wifi. This is NOT a bad thing for Nintendo to offer this OPTION. Why all the hate on it? No one's making you buy it and they're not pushing it as the "next hand-held generation". I will likely get a 3DSXL eventually once the game library gets a little bigger (though I will still keep my 3DS for sentimental reasons).
Why all the need for a second stick too? The current games don't have any need for it. The only game I can think MIGHT have benefited from it is KI:U which did better with the touch screen.