Haven't gotten too far with this game, but here's my initial impression in a nutshell:
After od'ing on Crysis/Crysis Warhead, this game is a refreshing respite. No aliens, no mutants, no irritating caves/mazes, just a straight out shooter with conventional weaponry. A machete, assorted pistols and machine guns that jam every so often. And oh, no nano suits.
As FPS games go, this game is not atypical. You are a soldier of fortune/mercenary sent to this beleaguered African nation to assasinate an arms dealer who plays both sides of two warring factions. So, really, nothing new there. But what sets this game apart from other shooters IMHO is the amazing realism of the environ. You can go from a lush tropical jungle setting to a a grassy savanna to a barren desert. While driving through a savanna, I was confronted by this herd of buffaloes. One actually charged into the jeep I was riding on. How realistic is that! I thought I saw some antelopes and zebras also. The geography and topography is just visually stunning. It's like being in one of those nat'l geographic travelogues, except that along the way, you have kill some baddies. The weather and time element is fantastic. The sunsets and sunrises are awesome to behold.
Another important aspect of this game, at least for me, is the open-endedness of the enviroment (unlike most fps). You are presented with I don't remember how many square miles of real estate, but it's vast and you are free to roam in any which way (preferably in a motor vehichle with a mounted machine gun).
BTW, if you don' have a super duper rig, you won't feel nauseated playing this game. With my opteron 165 with the 8800 gt, I can play on high and very high settings, 1920 x 1200, 2xaa @30-40 fps with no hiccups at all.
I highly recommend this game.