Microsoft have recently released ASP.NET Single Page Application (SPA)
some of them developed by Microsoft, and selected and packaged together.
so it is similar to Silverlight... That is to say not easy to start with,
but can handle more complex and "long running" applications.
There are useful SPA training classes
Online Demo (hosted on Windows Azure)
Looks very nice.
Unfortunately, most of the time problems solved with SPA
are similar as 20 or 30 years ago, "forms over data" for Enterprise.
And all this time, and huge improvement in hardware power,
apps development is still mostly manual process, relatively slow, hard and expensive.
And what would be a better way?
A "Domain Specific Language", more expressive and simple,
and is using whatever "runtime" is available and appropriate.
Focus on meaning (semantics), rather than on mechanics (syntax).
But foundation is very interesting, and evolving quickly,
so it is quite possible that soon enough there would be "wrappers"
that would hide details and focus on content...
In fact Microsoft also attempted something similar with "LightSwitch"
that started as easy forms on Silverlight, and later added HTML5 also.
Proprietary, but possibly more efficient for simple cases.