Whether it's labelled Silverlight, WPF or something else is secondary: Xaml and .NET is will be a first class development environment on Windows 8, as was shown today.
Tsutaya is not going to be happy. Considering how their shops always have piles of writable DVDs next to the cashiers, they obviously thrive on ripping.
Another possible issue, depending on your approach, can be how to integrate with external systems. I have seen teams trying to deploy a Haskell based common library to a heterogenous production environment and it wasn't pretty.
The core Haskell module itself solved a specific problem beautifully, but it all got very messy outside the confines of the pure and pretty functional world.