While I don't adore the title, I've yet to meet someone who doesn't enjoy playing Left 4 Dead. Though, even the most dedicated fanboys get tired of playing the same stale campaigns, and professional development studios can only churn out so much free content. Acknowledging this, Valve is preparing the release of Left 4 Dead's authoring tools.
The software development kit (SDK) is expected to arrive as soon as next week. This will allow users to generate new maps and edit existing ones as well as package content in a single VPK file. A new menu option named "Add-on campaign" will permit you to browse your third party content. Through this menu, you will be able to create games and invite friends to your add-on campaign. It will also aid in distributing user-generated content, by automatically offering your friends the option to download it.
With Valve's feet in hot water after announcing an early sequel to Left 4 Dead, this update should prove to be a band-aid. The main question of that debacle was whether or not the developers would live up to their promises of serving free downloadable content for the original. By releasing the official dev-kit, Valve's DLC shouldn't matter. The community can scratch their own itch by producing quality material.