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I've had it a year or so. I like it. I also played a lot of RISK as a kid so that's why. If you love RISK, give it a shot.
 
I downloaded the demo, and found it ok. I wanted a little more out of it (not as much as Civ tho ;)).
 
I used to play it a lot, and loved it. You should try out some of the story-line based scenarios/ campaigns if you want more depth - useful to learn about historical events too.

The AI can be set quite high, or play online for a nice community.

Similar is Dicewars:

http://gamedesign.jp/flash/dice/dice.html

Singleplayer, free, looks simple but has surprising strategic depth to it. I used to lose all the time now beat the AI 80% of the time on hardest settings.

For more challenge, I sometimes play the online muliplayer version, kdice, but it has a clunky interface and is slower so I rarely go there.
 
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