Pros: Fun, good multiplayer modes, original weapons
Cons: A bit short, cannot mix split screen and online multiplayer
The bottom line: I would recommend this game to anyone who owns a PS3
This was the first game that I got for my PS3. I have played the game many times and have beat it on the hardest difficulty level multiple times, both in co-op and single player, and I have to say it's a great game. The first thing you'll notice are the weapons. The weapons on this game are great, as they are more interesting than the standard weapons you find on many games. I'll list a few, but leave some out so as to not spoil the whole game:
Bullseye: The bullseye starts out as a standard gun, just shooting pellets forward like any other gun. However, if you right click you shoot a homing device. Suddenly all your bullets home in right on target, hence the "Bullseye" name. I love this gun; it's great for shooting enemies around corners, as your bullets can make the bend easily when on target.
Auger: The auger is an awesome gun. It's primary fire shoots blasts of energy that can shoot right through walls. This is great when you're on a floor beneath an enemy and need to shoot up to him. Of course this also can make it harder to escape an enemy!
Grenades: There are several types of grenades available. To begin with you have the basic frag grenade that is basically what you're used to with a grenade. However, you also get a hedgehog grenade that shoots out a shower of spikes on your enemy. THere is also a grenade that shoots a cloud of smoke that suddenly lights on fire to roast your enemies. The final grenade actually sheilds you from enemy fire.
Sniper Rifle: The sniper rifle starts out as a standard sniper rifle, with a scope to get closer in and large single fire bullets that can kill some enemies in one shot. However, the alt fire makes this gun a whole new level of fun, as it slows down time making headshots inevidable.
There are many other weapons, but you get the idea, the weapons aren't all just copies of every other game you've ever played before.

Gameplay: Gameplay is your basic first person shooter. You can hold a zillion weapons at once, and you gain more weapons by simply walking over them. You basically just see your gun (Except in cut scenes where you see your whole body). And the goal is the same, shoot all the enemies before they shoot you. You progress through the various levels by walking through a set path and killing everything in sight. There are cut scenes to give the basic story but you basically have the same story as every other FPS, shooting (which is what you want to do!) The enemies can seem a bit robotic at times, going in and out of cover at very repetative rates so you can just wait and shoot them like they're idiots. However, besides the way they come in and out of cover they have really good AI. I don't believe their movement is scripted, so you get a different battle every time you play.

Graphics: The graphics in this game are really pretty. However, if you dont have an HDMI cable and high def TV you won't see the clarity. You can appreciate the many polygons, but the clarity of everything is not evident. The people are very clear and everything looks crips. Seeing the detail on the shadows and all the objects are amazing. However, the most impressive part is the sheer number of things going on at once. You feel like you're in a real battle, with dozens of enemies shooting you all at the same time. At the same time debris is flying all over the place, with realistic smoke, etc. The sheer amount of things going on at once is really nice to look at.

Enemies: The enemies are not really the most amazing thing. They mostly seem similar to each other, and you mainly just fight against the same humanoid aliens over and over again. However, the "leapers" (Small scorpion looking creatures that "leap" at you) are really interesting as they swarm all over you. There are larger enemies as well, but nothing to really say much about, just expect typical ugly monsters to come after you.

Multiplayer: The multiplayer on this game is pretty good. There are two options. The first is co-op, where two team members can work together to beat levels. This is much more fun to me than playing single player mode. However, it is also much easier, as you only lose when BOTH people die. If one player dies then the other can come and "revive" the other. Also a timer will bring the other back to life. This makes it possible to go over and die many times over and still beat a level. This can be good however as it makes impossible levels suddenly possible. This is done through typical split screen. If the TV is a widescreen than the screen splits vertically, otherwise it splits horizontally. The other mode is through 4 player multiplayer modes similar to many other first person shooters. You can play capture the flag, deathmatch, etc. You can also play online with I believe 40 players (I dont play online much) This would be great, except you cannot mix the split screen and multiplayer modes. I find the split screen the best as I can play with friends instead of getting lost in the net.

When playing the single player (The best part of this game to me) you never "save" the game, it automatically saves checkpoints, and you continue from where you ended off. This can be annoying however, because you only get one saved game, so you can't share with friends. However, you can play levels already beat so you sorta can have two people beating the game at once.

My opinion of this game is that it is really fun and has great replayability. I wouldn't say you can play it hours on end withot ever getting bored, but for players who don't spend their whole days on their gaming system this game will last a very long time for them. The game is a bit short however, and may only last 12 hours the first time around, then 8 or so, down to even less as you get better at it.