Simply great fun. Haters are gonna hate for the childish art style, but it fits the game well and isn't really for kids.
Addition to previous review:
It's been a while since I've played a game that's just solid, pure fun. Most games try to jampack too much into it, or the community tries too hard to abuse every flaw. (Call of Duty, Sports game glitchers, etc.)
This game was the first game that I actually feel like I was having real fun with since Portal, and I really appreciated it. I had to go through the trouble of explaining this to explain why I gave this such a high rating. Ratings aren't about technical skill of the game, how flashy and fancy it is, but how FUN it is.