It's a full Ubuntu userland and you can even run graphical (X) applications. I've used it for Pebble development, running the (python + ARM GCC) SDK and QEMU-based emulator all on Windows. I've run into a few minor issues but for the majority of tasks it works great -- I've completely stopped using my Ubuntu VM and do all my Linux tasks in WSL.
The WSL has potential to become a very useful tool. So much so I'm considering switching from macOS on my next laptop or so. Unfortunately unlike your case, my workflow depends on a lot of networking code. WSL still has many gaps in the socket emulation pieces. It'll likely mature over time, and it's impressive that some people are already able to switch from a Linux VM!
A co-worker is also using it to run cross compilers for embedded linux hardware devices (various patched versions of GCC and such) and it's been flawless for him, which I found quite impressive too.