I'm kind of unimpressed with the 3 games I've put about 2+ hours into so far (Paper mario, 3d land, Zelda). I expected the hardware to be sub par so nothing on the OS really bothers me, although the analog stick is atrocious and my finger is constantly sliding off of it. It feels like how 360 sticks get after the grips wear off after months of heavy use.
My problem with the games is the same as it has been with Nintendo games since I grew tired of them many years ago...they're too simplistic. I'm not just talking (lack of) difficulty but they really do feel like games designed for kids. People applaud the gameplay only focus of Nintendo games but they don't offer any depth or challenge with their gameplay so there's nothing else there to boost the overall package up. Like 3D land for example, the main focus is to find those 3 star coins in each level but so far it's been really easy to do so, and after you do what's the point of staying and exploring each level? For useless coins? I already have 45 lives and I'm not even on world 4 yet. There's nothing to really do in that game and the actual platforming has been ridiculously easy so far.
And as for Zelda, only Nintendo can get away with rehashing a 20 year old world in a brand new game. I hope the dungeons are different at least.
If you want difficult games you should probably play Fire Emblem, Etrian Odyssey IV, Monster Hunter etc, not Zelda and Mario. Although I've heard that SM3DL gets fiendishly difficult once you "finish" it.