ArmA: Combat Operations is a frustrating experience that does not live up to its predecessor.
First, the good. OFP veterans will recognize the interface and gameplay. Indeed ArmA and OFP are practically identical in this regard. One big improvement is that you can now command squads larger than twelve men. The tilde key selects everyone, or you can select units one at a time with F1-F11, and you can use (I think) the F12 key to scroll to a second list that shows more of your squad. In the Mission Editor, I have placed up to twenty men in one squad, but I'm not sure what the limit is. Nonetheless, it is a vast improvement over OFP.
Speaking of the Mission Editor, it is great (arguably the only thing worth having in the whole game). Anything in the game can be incorporated into a custom mission. The scripting and such are very similar to that used in OFP, so those who edited the previous game should have no problem modding ArmA.
The concept behind the single-player campaign is interesting, though implementation of it is lame. There is a linear path of missions that carry the storyline, but for each one you can choose one or two side missions beforehand that are supposed to have an effect on conditions in the main mission. I've been unable to verify whether this is true, because it sure ain't noticeable if it is.
And that's the extent of "the good."
ArmA's graphics are horrible. It looks like the same engine that powered OFP, only improved just a bit. Had ArmA come out in 2004, it might have been passable, but even then it could not have stacked up against the likes of Far Cry. Foamy wave effects on shorelines are laughable. By default the game runs with some kind of "haze" effect that I guess is for realism, but it just makes everything hard to see (thankfully, it can be turned off). Some of the animations suck or aren't even logical, like your character going through the motion of reloading a LAW launcher, but there's no rocket in his hand.
Oh, and related to these pathetic graphics, the sound is awful, too. In the aforementioned LAW launcher scenario, not only is there no rocket, but the sound you get when reloading the launcher is the same sound you get when reloading a rifle. Did Bohemia Interactive's quality control people get stoned on testing day? Further, the same annoying "Go to ... tree ... at ... three o'clock" voices from OFP are back. They were okay in 2001, even cool, but now they're just annoying and sloppy. In the heat of a large battle, the voices pile on top of one another constantly and make you want to stab a screwdriver into your ears to make the pain stop. Combat should be chaotic, indeed, but ArmA's audio is just absurd.
The gameplay is ridiculously difficult. As with OFP, every AI player in ArmA is an elite sniper. No, I'm serious. These guys can take iron sights and shoot you in the head from distances at which most normal infantry would be hard pressed to hit a fifty gallon barrel. No exceptions. The AI's aim is superhuman, and it spoils the game at times.
As another OFP hold-over, the bots are as dumb as ever, gleefully throwing themselves in front of bullets for no good reason. They might be more intelligent than those in OFP, but we're really just talking about the difference between stupid and really stupid.
The single-player campaign, beyond the valiant attempt at innovation with mission selection, is a joke. There is actually a mission where you are dropped off in a town and ordered to demolish a bridge. Upon exiting the Humvee, you are given satchel charges and a rifle ... but no ammunition. After blowing the bridge, you have to run through an alley to some ammo crates, where you pick up a rocket launcher and some rockets, but there are still no magazines for your firearm. So you creep around and shoot enemy armor with rockets, and if you happen to come across any infantry, you are completely screwed unless you can kill them with a rocket and scavenge an AK.
Isn't this supposed to be a cutting-edge combat sim? Maybe I'm just ignorant about how soldiers operate, but I'm pretty sure they usually aren't dropped knowingly into a hot zone without ammo.
Other missions have similar quirks, but the bridge-demolishing one really stood out. Mostly, the missions are just way too difficult due to the previously mentioned AI sharpshooting.
Anyway, that's enough. ArmA: Combat Operations is not a good game. In fact, it's a complete waste of money. The flashes of brilliance that made OFP great do show up, but they have not aged well. What was new and interesting in 2001 is not new and interesting in 2007. It's a shame that fans of the old game had to wait this long, weathering a long conflict between Bohemia Interactive and Codemasters, only to ultimately receive an outdated, unpolished pile of junk like ArmA.