Rob Pardo, Executive Vice President of Game Design at Blizzard, tweeted that Microsoft's new OS is "not awesome for Blizzard either".
This week, Valve founder Gabe Newell called Windows 8 a "catastrophe for everyone in the PC space".
He feared that Windows 8 will be a closed platform for development thanks to the new Windows Store, which will sell apps for the new Metro UI and be the only way to get programmes onto the OS's start menu replacement.
Microsoft will also take a 30% royalty cut from every sale made on the Windows Store, meaning most developers will be reluctant to sell their products on it. Newell thinks this will result in losing some of the 'top tier' PC developers.
Windows has always been an open platform, allowing developers and programmers to flourish with complete control over their software, as opposed to the more rigid requirements of console gaming.
Windows 8 has been developed for both tablets and PCs, and Metro is a touch focused UI that will act as a launcher for programmes bought from the Windows Store. Windows 8 will release on October 26, but is available to download as a preview now.
Blizzard's next release, World of Warcraft expansion Mists of Pandaria, will come out later this year.
Watch a video for Microsoft's Windows 8 Surface tablet below: