If you are like me, and don't read the instructions and the readme files, you might encounter a few problems in getting the ADO.NET designer to work.
To enable the ADO.NET designer you need to install the ADO.NET EF Tools. But in order to install it correctly you have to install also the ADO.NET EF beta 3 and a cryptic XML Editor QFE in the right order.
So the correct installation order is:
Visual Studio 2008
XML Editor QFE
ADO.NET EF Beta 3
ADO.NET EF Tools (Dec...