Short and sweet but definitely worth the 5 bucks.
First level of each world is like a tutorial but after that the level of difficulty increases. Contains some very smart puzzles (some reviewers said it was frustrating to them) but it was ok for me.
It took me about 2 hours to finish the main game but the challenges can keep you busy for a long time (especially if your friends have the game too and you are competing with them for the leaderboards).
WATCH OUT: For that kevin dude. He is first on most of the level's leaderboards. Developer or not he is good :P.