The good news is that I saw no limitation on how old my previous VS version might be to get the upgrade. And if I didn't realy misunderstand them, I might even get it if I only "owned" the Express Edition!
According to a picture of the box on the U.S.A. page, the upgrade only applies to VS2005 and VS2008 users.

http://store.microsoft.com/microsoft...oduct/BE303EE9

So you should make sure of what the German requirements are before you buy it.