Well, unable to have an actual screen shot, so I'll have to draw it by hand...
So, you have opened a project in VS.NET Whidbey and you see in the solution explore the above 'image'. What do you see that strikes you as a bit, ummm, different? If it doesn't hit you right away or you see it immediately is irrelevant since I'm gonna tell ya anyways ;-) Whidbey is going to allow you to mix different source files that are written in different languages all in the same project! Yes, I said project... not solution like it is limited to today. Imagine writing all of your UI elements in VB.NET, your classes in VB.NET and C# and some interop (or cut-n-paste existing C/C++ [including inline assembler]) code ALL in the same project. Some people might not find this earth shattering news, but for me, this is freakin' incredible!
Also, it should also remove the need to have to resort to building modules and linking them together into a single assembly using the command line if you want to combine multiple language source files.