.NET4に対応したWindowsAzureGuestOS1.2が公開されました。
http://msdn.microsoft.com/en-us/library/ff436045.aspx
Configuration value: WA-GUEST-OS-1.2_201003-01 （←.cscfgに指定する値）
Release date: April 5th, 2010
Features:
* Enables HTTP dynamic compression for web roles
* Provides updates to the URL Rewrite Module for IIS
* Incorporates the Microsoft .NET Framework 4.0 release candidate
* Delivers stability and security patch fixes applicable to Windows Azure Guest OS, as noted below.