If this is indeed close to native performance, you wouldn't get anywhere close to that with a VM. I could be oblivious to some optimization techniques but Linux VM's on Windows have always performed drastically worse than native.
Now this does not render WSL useless; launch time for any random small tool is better with WSL than booting a complete VM, the memory is not partitioned, integration with the Windows Drive FS is slightly better, etc. But tons of use cases are better covered by a VM -- and with a huge margin.
Mate, the thing isn't even released yet and you're bashing it (excuse the pun) for taking too long to open up a man page? Give me a break.
After it's actually released and the performance gets better then it is of course going to trump running a whole VM and to suggest otherwise is just FUD, IMO.
I think Win10 is quite good, and that WSL is quite good given its age, and will be extremely useful for a lot of things.
Still, if you try some workloads, WSL is way slower than a Linux VM. I don't expect it to change for the release. I don't even expect it to change for the 2 years to come. Sill, of course, I could be wrong.
But even so; I insist: WSL is actually quite impressive.