I own the board game version of this, and was excited when I found it here on Steam. Zooloretto offers a fairly quick, semi-strategic game, with cute presentation. It is perfect for children and those who enjoy a good, casual board game.
The pros: quick easy games, with no setup; a moderately challenging AI; in-game challenges add to replayability; customized items and characters purchased with earned winnings; great "together" game to play with spouse and/or child.
The cons: AI is respectable, but not too difficult to manipulate; no online multiplayer (though this may not matter for some, like me); the soundtrack can get a little bit old after a while.
For $9.99, this game is a pretty decent deal, and almost anyone who enjoys board games will get their money's worth. For the $5.99 I got it for on sale, its a steal, and will see far more play than games I've paid substantially more for.