Microsoft dropped its alternative (Dryad) in favor of Hadoop. Next year they will release MS SQL Server 2012 with Hadoop integration. Azure and Windows Sever support is being developed even as we speak.
It will be available in the first half in 2012.
Hadoop is the #1 BigData platform and is going to be supported by opensource and proprietary source (Java, .Net, Python, ...) even Oracle is adopting it.
If you were developing something, you should wait if you're on the .Net platform.
More information about what is possible will be available here
Recently, MySpace released their .NET MapReduce framework, Qizmt, as Open Source, so this is also a potential contender in this space.
Also see this - See http://research.microsoft.com/en-us/projects/dryadlinq/default.aspx or http://msdn.microsoft.com/en-us/library/dd179423.aspx