Kororinpa is pure, unbridled fun, but that's because you can play the entire game 2-player and can do all the retries you want without having to worry about lives.
And you'll need those retries. This game is crazy hard in the later levels, and I can safely say that I enjoy it more than the Wii SMB.
However, I believe the laughter generated from watching each other fail and the subsequent tidal wave of profanity. The good news is that only one player needs to complete the level to progress and while the other player can still play for as long as they'd like to try, they can choose to give up and you can go to the next level.
Unlike SMB, you can actually tip the entire level upside down. With this tactic, you can skip large areas and find "shortcuts", but the developers saw this coming and placed gems around the level which you need to collect before the exit will open up. They also have waypoints which you can activate so you don't need to start at the beginning of the level every time you fall off.
I wouldn't recommend it as a game to buy, but it's an awesome rent if you have a friend to play it with.