Does anyone use this for work? Could I replace Ubuntu with Windows now?
That's a bit loaded, but I'll attempt to answer seriously:
Can you replace Ubuntu? Maybe, if you are OK with 14.04 LTS level support. Certain simple things straight up don't work -- you can't send a ping without an admin level windows shell (sudo wont do it either). You also won't magically get driver support for hardware that works in Linux, but not Windows (if you think this isn't a thing, try plugging in a random USB-to-something adapter without finding obscure, broken, or nonexistant drivers on Windows). If you just need access to some tools that only run on Linux, I've found WSL invaluable, so long as those tools are available on Ubuntu 14.04.
Can you replace Linux in general? Nope - I'm a 90+% Linux user for work and home, and neither Debian, Ubuntu, or its derivatives work for me, with the notable exception of some server and embedded applications. If you want a wide variety of up-to-date software, there is no replacement for something like Arch.
Can you replace Ubuntu? Maybe, if you are OK with 14.04 LTS level support.
The latest Creators update uses 16.04 LTS.
you can't send a ping without an admin level windows shell
The latest Creators update supports ping as a non-admin.
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I would say that for most usages it is a good replacement for vanilla Ubuntu. Microsoft is quickly closing the gaps in support. Most stuff simply works (albeit disk filesystem I/O is still a bit slow). For instance, I used it to compile packages for Ubuntu 16.04 and upload it to a PPA without much trouble. At the time the only change I had to make was using fakeroot-tcp rather than regular fakeroot. But maybe that is fixed now.
It is especially useful if you like to work in a Unix, but also need Microsoft Office, Adobe Creative Suite, or other applications that are not available on Linux.
I did know that, but the update only came out today AFAIK, and is being slow-rolled out (I checked all my Windows machines today, none updated). People with enterprise/business versions of Windows with "Defer feature upgrades" aka "Current branch for Business" enabled also wont get it for a while. I know how to force the update, but forcing Windows updates is something I've learned better than to do.
As an aside, I would highly reccomend WSL users check out wsltty[0]. Gives a better terminal than Windows' built-in 'cmd', with options to open other shells like fish/zsh/etc in arbitrary directories.