Hi Theron Kousek,
The best version of Blend to use depends entirely on the environment you are working with.
The latest version of Microsoft Expression Blend is 4 and it creates Project and Solution Files for Visual Studio 2010. Thus, if you are using the latest release of Telerik controls but working with Visual Studio 2008, then the most appropriate is Blend 3.
If you are using Visual Studio 2010 and Silverlight 4, you would rather work with Blend 4.
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