In-Process Side by Side (Part1)
Luiz Fernando Santos talks about a .NET 4 feature called In-Process Side-By-Side which will allow multiple versions of the .NET CLR to be loaded inside the one process. This sounds like a great feature, as I remember the problems with IIS using ASP.NET 1.1 on a server with .NET 2 also installed, and .NET based COM components trying to load .NET 2