It's a good... well, quite good turn-based strategy game in full 3D.
I would say it's quite realistic, with troops reacting to enemy fire, huge importance of the terrain, and good multiplayer support.
Just don't expect superb graphics.
It's one of my favourite wargames, but behold! they are working in Combat Mission 2 right now
This game was supposed to be Close Combat IV (if I remember the number correctly) but Microsoft thought it didn't have the looks they wanted and cancelled the association with the developers, who went on to distribute the game themselves (luckily!)
Since I think it will be sometime until they release CM2, my advice is "buy it!"
Daniel, aka Cyrano