I bought it and played it a bunch.
It's very polished. The campaign is 5 levels and it has cutscenes which are well done and pretty funny. The cutscenes are probably the best xbla has to offer in animation.
The different maps have map specific things. One has cities that give you extra units, one has a missile which gives you a bonus to attack in that area, one has a damn which lets you flood an area, etc
The campaign is easy to hard (depending on how you roll). I played about 10 skirmish games against the AI and lost them all. It's sorta funny because i played a lot of risk and castle risk when I was younger. The skirmish computer is hard, so newcomers will get frustrated and stomped. The AI does have some oddities, on the classic map they like to clump up their capitols (especially around Australia), which can make a certain corner of the map key to victory. The AI tends to skirmish nonstop, but then somehow 1 of them quickly becomes dominant and nearly unstoppable. A lot of the games I was in 2nd place (more or less) and the other AIs were trying to stop me and not the 1st place player.
The objective system is very interesting. Each time you play you get slightly random objectives (e.g. take over North America). Once you complete an objective you get a moderate to awesome ability for the rest of the game, and then no other player can complete it. If you finish 3 objectives you win. Sometimes it seems like going all out (playing RISKY) just to finish an objective is the way to go, even though you might get beat down the next turn.
Haven't played online yet, so not sure how well that works.
So it seems like a great adaptation of Risk, you just have to be ok with not coming in 1st place due to die rolls + ai/players teaming up on you.
