Well, not all of it, but Microsoft has made it possible to enter the .NET Framework code when debugging. Although configuring Visual Studio to do this is a little more work than what you need to do with, say, Java and Eclipse (which is: none), I believe it is still quite a useful feature. It allows developers to go into the code of the .NET Framework and see what’s happening with the objects that are passed on.
I have yet to test it, since I have Visual Studio 2005 and it’s only available for VS2008, but I hope to get 2008 somewhere in the future.
Anyway, it’s a little buzz on blogs here and there. Be sure to check out Scott Guthrie’s post on it, where he mentions which namespaces are available for now, and which are planned.