This is probably a fair point about the "enterprise .NET" community, which is by nature very conservative and closely aligned to core Microsoft technologies where the guarantees of support are strongest and the developer pool the largest.

However we as a smaller shop have used F# on a couple of projects within the last year -- to embed an expression engine within an analytics product, and for the parser/analyser in our Sass plugin for Visual Studio. But I know I'd have struggled to get that technology choice into the last enterprise environment I worked in. So the lack of uptake may be more to do with the culture of "enterprise .NET" shops, more than the "broader .NET community."