"Just how long Left 4 Dead will last for you remains to be seen. As enjoyable as the online portion of the game is even after multiple tries thanks to the "Director", killing thousands of zombies in the same setting can get a little tiresome after a while. Hopefully Valve are gearing up to offer free/cheap downloadable content to add more weaponry/scenarios to keep us all gripped for the long winter nights.
There's little doubt that Left 4 Dead is one of the best co-op games out there at the moment. With four of you battling the zombie hordes, there's little gaming experience that offers just as much in the way of fun time thrills.
But, if you plan to stick to the offline game all on your lonesome, you're best giving this a wide berth."