As primarily a Linux developer a Windows developer commented on C# and some useful RPC functionality. So I had a look and it seemed to sort of work.
There were obviously massive gaps in the functionality between .NET and Mono so I monitored the progress of Mono on Linux.
It soon became clear that with the creation of Xamarin then Mono on Linux wasn't really going anywhere. I am of the opinion that de Icanza is a politician. He'll tell you what you want to hear but if something better comes along he'll go for it. I don't blame him for furthering his career but it's not because he is a great coder or really committed to open source.
I don't believe the open source team were always talking to the .NET guys because why would Mono have so many deficiencies. de Icanza may have been talking to MS but I don't think it filtered down to open source but de Icanza used this to get to where he is now. Just like a politician.
I have found the views expressed here to be quite enlightening. I thought it was just me!