This is big news. I don't really have an opinion about this one way or another just yet...I haven't had time to read all the details. Reflector has always been the freeware tool that .NET developers use to figure out how internals work and it had a nice add-in story - I hope that continues in the future. It'll be interesting to see if a pay-for version comes out in the future that's side-by-side with the freeware version, and if someone in the .NET community starts up another freeware tool like Reflector (it won't be me - I don't have the time!).