Treyarch has explained to the Call of Duty: World at War community why patching the PC version has taken so long.
This process involves listening to fans, reproducing the issues to engineers, testing, submitting the patch to Activision, more testing, and then finally building an installer and distributing the files.
"The minimum estimates of time listed above are best-case scenarios, and on average, it takes longer than 2 months. In rare emergency cases, this time can be trimmed down, but this is very rare, and depends on what is being addressed," explains JD_2020, who could be a robot with lasers for eyes.
He goes on to explain that hot fixes (title updates) familiar to Xbox 360 or PS3 owners are not possible on PC, as there's no overarching service such as Xbox Live or PlayStation Network to take care of them. Valve and Microsoft might disagree.