The first issue that I ran into when testing Entity Framework Beta 3 and the designer is related to the fact that the designer is not supported on 64-bit systems. The problem is that the build action for the edmx file isn't run properly so the csdl, msl and ssdl files isn't created in the output directory. Fortunately this is easily solved by copying the Microsoft.Data.Entity.Build.Tasks.dll and Microsoft.Data.Entity.targets files from the Windows\Microsoft.NET\Framework64\v3.5 directory to the Windows\Microsoft.NET\Framework\v3.5.

I also had another issue, that the generated code does not follow Microsofts own naming guidlines. This is something that I have been suprised by before, and I thought that new tools coming out wouldn't result in complaints from the static code analysis anymore.