With a short, shallow campaign and repetitive multiplayer, Left 4 Dead is fun while it lasts, which sadly, isn't long.
Singleplayer:
You play as one of the four survivors who are trying to escape the zombie apocalypse; Francis the macho, hard hearted biker, Bill the veteran war hero, Louis the average civilian and Zoey, the hot college girl. There is no difference between the players except for dialog.
The core gameplay is this: Get from point A to point B while shooting any zombie on sight...that's pretty much it. The problem that I found with L4D is that it is extremely repetitive. Shooting zombies over and over again with the same weapons gets old. Once in awhile you'll came across a crescendo event- a climactic moment in which you must fight off hordes of aggravated zombies until an obstacle is removed from you path allowing you to progress further. These moments are fun while they last, allowing you to cooperate with your teamates to try and survive.
The game has a unique A.I director in which it will place a super zombie (or "special infected") to attack players depending on how well they are doing. You have the
-Boomer, an obese zombie who will vomit bile on players, temporarily blinding them and attracting a horde of zombies to attack.
-Hunter, a fast and agile zombie who can leap great distances to pin players down while ripping them apart, making them helpless until another player manages to get them off.
-Smoker, a zombie with a long, whip like tongue that can constrict players from afar and drag them away from their teamates.
-Witch, a female zombie with long claws who attacks only when provoked. She is capable of downing a player in a single strike.
-Tank, a huge, muscular zombie. Considered the strongest and most dangerous of the special infected, he can cause some serious damage to players with his powerful punches and boulder throwing attacks.
It is fun killing these special infect and it does help break up the repetitive pace.
The entire game can be finished in 3-4 hours, there are only 20 maps (which are also used for the multiplayer) and only 5 different weapons to use. I found L4D to be very poor in terms of value.
Multiplayer-
With the mp, you'll be able to play as the zombie special infect, taking a whole new approach to the game. Instead of going rambo you'll have to approach a more stealthy tactic to ambush the survivors. It is quite fun playing as the SI, whether it is tearing up your enemies as the hunter or vomiting on them as the boomer.
The problem though, is that the SI have far less health than the survivors, so they tend to die much more easily and frequently. This wouldn't have been a problem if the game didn't have a 20 second respawn time. I understand Valve did this to keep the game balanced, but I can't help but feel like I could have at least been doing something in those 20 seconds instead of just being idle.
Conclusion- All in all, Left 4 Dead is a fun game if you have dedicated friends ready to play with you. But for someone like me, who spends a lot more time playing the singeplayer, I find it rather short, shallow and repetitive. Once you've finished the 4 hour camapign you've pretty much finished the whole game. There are no extras to unlock, bonus maps/ weapons or anything like that. It's a great game if you are an online, multiplayer type of gamer who enjoys gaming with friends though.
My advice: rent it first.