Now it looks like I can freely exchange my files between the WSL and Windows. Is it true?
Do I finally have a linux inside a windows machine where I can install things using apt-get (instead of cygwin setup.exe)?
When will it goes into the official Windows 10 version?
You can easily read/write Windows files from Linux, but I don't think you can do the opposite. I've used git within WSL to drive a repo on my Windows drive.
WSL gives you full-blown Ubuntu 16.04 where you manage packages with apt-get. You have to look close to the bare metal to see differences. Until the creator's update, for example, ifconfig didn't work.
Earlier today, I compiled and ran some OpenMP-based code in WSL and it happily detected all the cores on my dev machine and kept them busy with worker threads. Pretty cool!
The bug report I filed suggested that this was being fixed soon.
Cygwin is still useful.
You're not supposed to access the Linux filesystem from Windows -- it's in a system hidden area of your profile but some people still tried to mess with it with unfortunate consequences.
I know that apt-get works since earlier instead of the terrible Cygwin distribution model, but yes, IIRC there are NTFS streams being used for the Linux file system metadata IIRC and if these get overwritten or somehow modified things go bad. And NTFS streams being a somewhat uncommon NTFS feature, some applications don't handle them well?
On the other hand, wasn't a new Windows 10 Creators Update feature that you could now indeed edit the files from Windows, and not just from the Linux subsystem? And that the Linux tools such as web servers are now even notified when the files change so they can reload them automatically? I'm not sure how they solve the metadata borking issue though, in that case.