Tim posted something on Facebook recently (I think in the last couple of nights) hinting that some big news was possibly coming: I assumed it would be Microsoft related. So this morning I looked through my feeds and both Scott Guthrie and Heuer dropped "it" in public. The .NET Framework source code will be released under the Microsoft Reference License later this year.
Holy c%@#! Debugging without having to use Reflector is significant: yes, some of us have to do some spelunking from time-to-time. And - well Scott says it best towards the end of his announcement:
Having source code access and debugger integration of the .NET Framework libraries is going to be really valuable for .NET developers. Being able to step through and review the source should provide much better insight into how the .NET Framework libraries are implemented, and in turn enable developers to build better applications and make even better use of them.
Great job developer division!