I started doing C# development last year, coming from mostly a Unix/Perl platform, and I'm really glad about the timing because that's when Microsoft got serious about open development. I started doing web apps using ASP.NET MVC3, and this year MVC4 was released as an open-source project[1]. It seems that a bunch of 'young turks' have reached higher management positions in most of the key software development products within Microsoft and they're all pushing for this kind of open source approach.
[1] http://aspnet.codeplex.com/