If you remember when we first caught wind of this game, I got a little excited. A co-operative shooter set in a zombie apocalypse? Yeah. Now...I'm a little more excited. The first details about the game have surfaced from a Q&A the developers submitted themselves to with GameSpot, and among the highlights are:

The initial four campaigns of Left 4 Dead include both urban areas and rural areas, with lots of dense architecture and challenging landscapes. Each campaign also ends with an elaborate "finale" where the survivors must make a stand while waiting for a rescue vehicle to arrive and take them to apparent safety.

The experience of playing an infected is entirely different than that of being a survivor. The four "boss infected" classes have very unique abilities based on their particular virus-induced...mutations. For example, the boomer can vomit blood on his victim, which attracts hordes of infected to this victim.

But the infected cannot use items or fire weapons, and will die quickly if they blindly charge at the well-armed survivor group. That said, the infected are legion in number and when one dies, they spawn right back into the fray after a short time. The infected just keep coming. As such, playing as an infected tends to be more of a "hide and seek" kind of thing. You want to position yourself to attack at the worst possible time for the survivors, lurking and stalking for a bit until you make your move.

Left 4 Dead is built upon Turtle Rock Studios' next-generation AI technology. This lets us create a scalable game experience whether you play alone with AI-controlled survivors and infected, or online with and against human players.

We are planning to continue to create and release new content for the game via Steam, much as we have done for the Counter-Strike franchise. Over time, we expect the inventory of items in Left 4 Dead to continue to grow.

And finally...

Allowing the PC and Xbox 360 versions of Left 4 Dead to play together is something we're still investigating.

It eludes me why this game isn't getting more press. Co-op, shooter, blood-vomiting and zombies? That's pretty much everything you need right there, except for maybe a pirate or something. Luke Plunkett

Left 4 Dead Q&A - First Details [GameSpot]