If you got as little as five minutes of fun out of this game, it would be worth it. Even if you hate the strategy genre, there's very little reason not to give this a go for such a low price.
Dont worry about no key assigned seems its happened to a lot of people including my friend. He rang MS who said its due to the high demand the server is behind on sending keys out and you will get it within 72 hours. He bought it last night and got it an hour ago.. So nearly 24 hours for him.