F# is quite fast (I've written a good deal of F# code) and it has seen a big uptick in adoption over the last couple of years.
I had a look at the F# code and it's not all that efficient (there are a number of intermediate data structures being created that don't need to be). I'll have a go at optimizing the code to see if I can improve the performance.
I find this a bit odd. Microsoft should be able to build a better compiler. I thought F# was getting a lot of traction.