MSDN: List of Breaking Changes .Net 1.1 -> .Net 2.0
Here it is a list of Breaking Changes reported / noticed by Microsoft when porting applications to .Net 2.0
http://msdn.microsoft.com/netframework/default.aspx?pull=/library/en-us/dnnetdep/html/listofbreakingchanges.asp
Breaking changes are changes in either the .NET
Framework (runtime breaking changes) or Visual Studio (design/compile/project
upgrade) that make certain application and development scenarios behave
differently. These are not necessarily changes that we have found to impact an
application, rather these are changes in behavior discovered during design
review and testing that could potentially impact an application. In all of our
application compatibility testing, we've found fewer than 10 of these impacting
an application.