(Addendum) I did a Fast Ring update on a separate machine and did not see substantial performance improvements, but the comparison is not valid between the machine linked and the machine I tested on, so I'd be hesitant to say that the performance hasn't improved at all, just that IO performance is definitely a weak point to WSL.
We have some improvements coming in Creator's Update and more substantial improvements planned in future releases, once we've completed some work with the NT kernel filesystem team.
