>To even write unit tests effectively you need to write your code in a certain differently.

>In C# this normally means using IOC + DI.

I've become quite partial to functional programming in the last few years. Side effect free functions with functions as interfaces for DI lend themselves perfectly to TDD and data parallel async without worrying too much.

C# is now slowly taking over most of the good features from F#, but I think the culture won't transform so easily.