Visual Studio's Edit and Continue and other IDE's equivalent operations are very effective for experimentation in interactive applications, since you don't have to restart the app to see the effects of the code change (most of the time). If Visual Studio already supports this for C#, then why isn't it in F# yet? Does something about F# make it more difficult?
It boils down to the fact that this kind of feature needs support in the compiler itself, and since the F# compiler has a much smaller team working on it than the C# compiler, they probably have other, higher priority items to work on.