I had other interviews and was not 100% prepared for reviewing my task, but pay attention to performance and encoding issues. I also got Async / await internals related question. Overall, I did ok. I know ASP.NET MVC to some degree. But it seemed like they were looking for someone who knew web-apps and .NET at expert level, not someone smart who can learn which may speak to the problems they need solving. Interesting experience, respectful, a bit long. The debugging questions were in the form: Foo is happening when run from this machine, but not locally or files can't be accessed on IIS server, what do you think is the problem and you can ask questions etc. They were real issues they encountered but weird edge cases, for which the answer is probably not so important as the steps you'd take (for MS-SQL issue for example)
In summary, looking for ASP.NET MVC / SQL / .NET expert.
They politely told me that they didn't want to move to next level. It was a fun, challenging experience but if they had stated they were looking for expert level, I'd probably told them I wasn't an expert and asked them if they want to proceed at the beginning.
Also, the gap between stages was kind of long (2 weeks)??