My hypothesis is that other half says:

* Code is less clear than C style (type inference, not used to some pervasive operators like function composition or piping)

* Code is terse and short names are more prevalent (Lost the way to kingdom of nouns)

* There is no Resharper support, and Visual Studio (the main IDE with F# support) tooling is not as advanced as for C#, which is impairing to some extent if you look use the language like a glorified C# and not too used to F# way (tooling is great compared to many other languages IMHO)

* There is no do/while or goto or break