This version represents a major break in the way the .Net runtime is distributed. In the past, each new version of the runtime was offered in conjunction with a new version of the Visual Studio IDE. The third major release will continue to use Visual Studio 2005.
Microsoft is currently planning on a final release in conjunction with Windows Vista. In the mean time Microsoft is not allowing production use without a Go-Live license. While this can be obtained free of charge, it doesn't allow distribution of the runtime. This pretty much limits it to web servers and internal use.