While the singleplayer is lacking compared to the multiplayer experience...that does not make this game any less fun.
(Note: I have the Collector's Edition, which comes with a DVD with a theme, some gamer pictures and some other goodies...but I recommend getting the regular version if you're on a budget)
Gameplay:
The enemies in Perfect Dark Zero range from total drones to master blasters. There is really a lot of slack in how they act. Sometimes they are worse than Storm Troopers in Star Wars, and other times they are sniper elites. I can't even count how many times I was shot at before I even saw enemies on my screen. This also goes for the bots in multiplayer. Sometimes I get my ass totally handed to me and other times the bots just run around like idiots. The inconsistency of their actions is my main gripe with the gameplay. There are tons of weapons to choose from, each with a distinct 'personality'...But it will really all come down to personal preferences.
While some may rag on the game for the lack of a jump feature, and I will admit it is kinda silly, once you get used to the controls you probably won't even notice. The dodge button isn't quite the same, but it shares the same purpose. Controls are fairly straightforward and simple. One of my favorite features is the variable zoom by how hard you squeeze the left trigger. Aside from that addition, not much else is new.
Multiplayer is a whole different beast. With tons of fun modes to play, some familiar, some not, there is a ton to enjoy here. DarkOps modes are different from most standard modes found in FPSes and several of them (Infection, mainly) are quite fun. I wasn't a huge fan of Halo 2 online, but I cannot get enough of PDZ.
Graphics:
Though everything has an odd shine to it, most of the graphics look quite good. Most noticable are the bricks/tiles that all have a distinct look to them. There is a lot of variety to the places you'll play, and they all look pretty damn great. The character models, on the other hand...yeah, not so much. Some weird hybrid of anime and realism, the characters all look pretty damn horrible. It's quite odd considering how realistic the environments and weapons are. They don't look bad, the clothes they wear look great...it's mostly their faces just look strange.
Sound:
The guns all sound top-notch and the in-game music is pretty sweet, as well. In multiplayer I usually had a custom playlist going just to add something new, though. I got kinda tired of the techno tracks that are prominent. The sounds in the environments, and most of the sound effects are quite good. The voice acting ranges from over-the-top to pretty lame. It's hard to tell which is funnier, the dialogue or the acting in a lot of cases.
Value:
Singleplayer campaign is longer than I expected. It took me around 7 hours on the easiest difficulty to go though. For the achievements, you may want to go through on some of the tougher ones, though. Co-Op mode really stands out as sheer brilliance, though. Rare really nailed it with that one. It is seamless to play with another player and in most cases, works even better than playing by yourself. One player is always Joanna, while the other player will play one of several characters.
Multiplayer adds a damn near infinite replayability to this game. Simple deathmatch (or Killcount, as it's called) is fun in itself, but the other modes found in the game are also great. The achievement system is mainly for online play, which adds to how much you want to play, as well.
Reviewer's Tilt:
While I approached this game with cautious optimism, I walked away greatly surprised and greatly satisfied. There are flaws, to be sure, but the overall package is solid. If you have Xbox Live, this is, in my opinion, a must-have game. If you don't have XBL, you might feel a little shorthanded, since the game doesn't excel in the singleplayer mode.