Well, I can't answer for Stronico, but we use a similar stack (Visual Studio 2010, Windows 7 / Server 2008 R2) for development and ASP.NET MVC 2 / IIS / SQL Server / Azure for our website. Using something else wasn't even really a question, since our product is .NET-based, and I'd already had a few years of experience as an ASP.NET dev.

I'd bet that nearly all of the other startups using a Microsoft-based stack have a senior / lead developer who has a significant amount of C# / .NET experience.