It's a good game, although it would be nice to have some connectivity in there, such as uploading your highest scores. However, something else missing is any explanation of how to play Yahtzee well. Yes, there are tutorials, but they just tell you the mechanics. It would be good to have more tips on Yahtzee strategy, for those who spent their childhoods baiting Uncle Fred rather than honing our dice skills.
Still, Yahtzee Adventures International is a good example of a casual iPhone game with broad appeal that's had some thought put into its structure and presentation.