As to the first poster, I say go with it. It has problems, no doubt. Some skills and augmentations are near useless (I personally dislike the concept that ballistic weapons cause more damage the more I spend skill points in it; I'm not too keen on the concept that my bullets are gaining strength
neither do I like the fact that my heavy weapons instantly lose their weight because I train in them). Multiple paths trough levels are more often than not unimaginative or vent-centric. Your decision making doesn't change the game in any important way except on the very last level (yes, decision-making is
that canned). Enemy AI is usually hit and miss. Your actions don't really matter much to others unless you're dealing with scripted actions. Clues to get past certain things, like keypads and computers are usually easy to understand for yourself, and easier to find lying around. There are also some other elements which are contrived, such as finding a merchant of sorts selling items, killing him, and realizing that he doesn't have anything of what he was selling on his corpse. The game loses its initial gripping feel somewhere at the middle of it, it just feels Ion Storm just wanted to give us more levels in which to try out cool gameplay gimmicks without realizing it starts to drag unnecessarily. Dialogue is good, but most of the times, you just have to read it, as the dialogues are mostly automatic and dependant of whatever you do (or don't) in the past. It doesn't allow for a good implementation of selecting dialogue lines. The story sometimes even suffers with this.
Still, the voice-acting is actually good in some cases (though truth be told, its flat out mediocre in othes). Stealth is somewhat well-implemented, and it's quite possible to end the game without killing more than 3 people (and there are ways to even avoid killing them by use of weapons, too). If you invest in combat, it can also be rewarding. Weapon mods allow to improve weapons (increases in range, recoil suppression or scope mountings are some examples). Some of the game's moments are interesting, and AI barks are sometimes hilarious. The ability to handle defense systems is good, along with hacking ATMs. The world is well crafted. One of the better elements of the game, and perhaps because of itself, the worst, is that you can gather much information from browsing computer files and message boards, or even from reading datapads, which helps build the gameworld; problem is, you can't really do a damn thing about most of what you read, specially things that affect UNATCO. In fact, one example would be finding out about a target you are instructed to eliminate, yet, when someone mentions him to JC, he acts as if he's never heard of him.
To keep it short, it sucks as an RPG. It succeds in being an FPS, if you invest some time in weapon skills. As a FPS/RPG hybrid, it works.