I got Pix3D (from the European eShop) and so far I like it. It's a cool concept and it takes advantage of the 3DS hardware. Circle pad and stylus controls are equally good. The 3D feature is nice (I adore the glasses-free 3D and would like to see more games that utilize it fully).
I also appreciate that the shapes appear in a different position every time you replay one particular puzzle. So it's not just a matter of memorizing the solution.
Ducutzu