Well, the last few ratings are not that positive. But they are from januari 2013. Indeed the game crashed a lot back then, but since they fixed that, I never had any troubles with opening this game. This game deserves a medal since it releases new monsters all the time, they also give you plenty of chances to earn diamonds (so you don't have to buy anything). Also, this game is quite old, so it's not a "copy" of dragonvale.
There are some troubles with completing missions, since you meet the requirements but the mission does not turn to complete.
Still, I love this game and play it every day for almost two years now!