There are not too many bad things about the game, but the only one I can think of makes buying the game questionable:
When you play the game to it's limits, as in defeat all of the challenges, the game loses its fun considerably. You can only play it so many times until you find yourself in a cycle of repeating events. Most games are like this, but this one does this faster than most.
In We Ski, you play a character (either one you create on the spot, or one of your Miis). Your character travels to the Happy Ski Resort, a virtual ski resort full of winter fun and many adventures. Here, you can try your luck at the slopes, trying for the best score on each course. You can go to the Ski School to help you learn the ways of the game. You can even interact with the other characters in the game to achieve goals and conquer challenges. You can take pictures with your characters, too, and make a slideshow with them.
Sounds a little cheesy. But with the main storyline and the Pros and Cons listed above, I'd give this game an overall rating of 75%. 90% for the good, -15% for the bad, and just 10% for just being there to be entertaining.