Far Cry 2 is competent, but nothing more
Far Cry 2 is a game with a lot of good ideas, many of which simply are not well-executed. While the basic shooting action is enjoyable, the context in which the shooting takes place is often frustrating, boring, and filled with questionable design decisions.
For example, the enemy checkpoints positioned at intersections throughout the map seem like a good addition to the game; they break up long drives and often have useful item caches or diamonds (the currency of FC2). The problem is that these checkpoints are entirely too frequent. I found myself having to leap from a moving vehicle every 30 seconds or so to clear another checkpoint, sometimes forcing me to expend all or nearly all of my ammunition before I could even reach a mission objective (which always involves more shooting). Infuriatingly, although you can "clear" checkpoints by wiping out the enemies and thoroughly searching the camp, the enemies there will respawn within minutes. This means that you might clear a checkpoint on your way to a mission, and then fight back through the same one on your way back. Why have the option to "clear" a checkpoint if the accomplishment is meaningless in terms of gameplay? Why bother having such a large, open map if you're just going to pack it with encounters that halt exploration?
The random encounters with enemy jeep patrols are just as problematic. And make no mistake, there are no non-enemy jeep patrols in Far Cry 2, because every NPC with a gun is an enemy. There are exceptions: your two AI buddies (who rarely do anything to help you, but do require that you help them pretty often), and guards in the cease-fire zone (who are essentially window-dressing, unless you shoot at them first). There is a flimsy plot-related excuse for this, which is essentially that "all these missions are top-secret and not even our men know about it!" or something equally silly. All this really means is that Ubisoft didn't want to have to implement a system for keeping track of who you're helping more.
This is another great example of a cool idea poorly executed. Having multiple factions with which to interact in the game seems like an interesting idea, but if both sides are always hostile, the inclusion of multiple, basically identical factions seems pointless. Additionally, each mission provider will always give the same type of mission - gun dealers always send you to blow up a truck driving in circles, the armies will always make you blow something up, after which your buddy will need to be rescued, and the underground resistance members always want you to liberate a base somewhere, etc. etc. It seems odd that there would be so many missions from each provider when they never offer any variety. Because each mission was so obviously created with a template, the large number of missions seems like a publisher decision to make the game longer artificially, so length could be added as a bullet point on the back of the box.
There are multiple unlockable upgrades for your character and weapons, many of which are stealth-based. The game even goes out of its way to point out a stealthier option on occasion. But why bother spending 45+ diamonds buying a camoulfage suit and silencer when enemies will spot you from a mile away with or without it?
Another example: there are cases with diamonds hidden throughout the map. But these aren't particularly fun to find (there's a minigame that amounts to playing "hot and cold" with a blinking light), there are somthing like 120 of these to search for, and they only contain one or two diamonds each, while a single mission will sometimes pay more than 20 diamonds. If they're not fun to find, why have so many? If the reward is so poor, why expect players to want to look for them? These are the questions Ubisoft should have been asking during development.
It's a good thing that Far Cry 2's basic shooting mechanics are as much fun as they are. With the exception of some weapons (specifically the G3 you start with) being terribly underpowered, many of the weapons have a good punch and are generally fun to use. The healing mechanism is sort of novel and the fact that reloading, healing or picking up items manipulate the character's head (in a Killzone-like way) make the experience more immersive. If only the developers had put more work into eliminating the frustrating bullshit in the game world that serves to ruin that same immersion.
Unless you are dead-set on playing this mediocre African excursion, don't bother. There are just too many great PC shooters to waste your time or money on Far Cry 2.