I have been playing this game (single player mode) for 3 years now.  It is the 2nd best game I have ever played (Deus Ex is the best), and the best stratagy game I have ever played.  The graphics are great, and the sound is truely awesome (though some sounds can get monotonous if you have all sounds enabled).  The narration at the beginning of each mission is as awesome as it would be if the man who played Darth Vader did it.  It is very addictive gameplay which will perhaps give 100 hours or more of addictive fun.  It was very hard for me at first, but after a week or more I became very good at it on "Hard" skill.