I tried the demo with my daughter, who's 6.
I have mixed feelings about it. The game was pretty, and had charm. The characters were definitely appealing to my daughter. The backdrops were gorgeous, and there were nice clean menus. But, I can't say we were having a lot of fun....
First of all, controlling the little light blob isn't very exciting for the second player. I appreciated the clean combat system, but didn't appreciate how many hit points enemies had, and how slow and drawn out the fights felt. The skill tree felt pretty unnecessary, tbph. The dialogue was meant to be story book, but overly forced with its rhyming. Puzzles felt overly simplistic to the point of having no purpose (especially since we recently completed Trine 2, which has excellent puzzles)... making exploring pretty boring.
I want to like the game, since I appreciate what they were trying to do. The game has a strong sense of elegance to it. But at the same time I think there's evidence there that this one might be over-praised.
There's a hipster trend right now where anything artsy and pretty gets good reviews, for the most part. But doesn't a game also need to be fun? Am I missing something? Because I was bored out of my mind.