Sven, I'd suggest you open up, and avoid what I call the Microsoft ghetto. I'm not talking about server-side technologies here, use ASP.NET AND C# as much as you want (you're only hurting youreself ).
I'm talking about the disconnect Microsoft developers have with current client-side libraries/frameworks and JS tools in general. I think they still need the nod from mother Microsoft in order to use anything, and god forbid they use anything from arch-rival goog.
That seems like a rather weird statement. Not only does the default ASP.NET MVC include jquery, modernizr and knockout, VS2012 actually supports knockout's data-bind attribute and provides some autocompletion for it. Not to mention that pretty much any other library or jquery plugin you need is only a few clicks away with NuGet.
So it looks to me like the current generation of MS web tech has fully embraced the modern client-side libraries. Not to mention that ASP.NET itself is open source as well.
I'd say at least 90% of the perceived improvement in web development for me comes from the tooling. The fact that I don't have to go hunting the web for libraries and then figure out how to integrate them into my stuff is invaluable. And JS intellisense actually seems to work pretty well in this version, which helps a lot.