A recent announcement that Microsoft is Open Sourcing .Net got slashdotted (http://developers.slashdot.org/developers/07/10/03/1626209.shtml).  There has been speculation from personal blogs (http://weblogs.asp.net/fbouma/archive/2007/10/04/don-t-look-at-the-sourcecode-of-net-licensed-under-the-reference-license.aspx) to industry pundits (http://www.eweek.com/article2/0,1895,2191754,00.asp).  But I think the most insiteful posts were from Microsoft’s Open Source website - Port 25 (http://port25.technet.com/archive/2007/10/03/releasing-the-source-code-for-the-net-framework-libraries.aspx), which states that the debugger will be able to step through the code.  As well as Miguel de Icaza (Novell’s Open Source .Net implementation) blog post (http://tirania.org/blog/archive/2007/Oct-03.html).