At this point in time, there’s only a single release available to customer of Windows Azure operating system version released on Dec 17th, 2009, but the promise from Microsoft is that new builds will be made available on a regular basis. “Customers can now choose when their applications receive new operating system updates and patches by selecting which version of the operating system their applications’ll run on in Windows Azure. This new feature allows developers to test their applications when new patches come out before upgrading their production deployments. To select an operating system version for your application, add the new osVersion attribute to your service configuration file. The full list of available operating system versions is maintained in the Configuring Operating System Versions topic in the Windows Azure MSDN documentation,” revealed.