The WinBtrfs driver has kept making progress since we originally wrote about it at the start of the year. Over the summer it picked up some new features and now it's out with a new release for those using Btrfs on Windows.
WinBtrfs 0.7 adds support for RAID 5/6 Btrfs modes, seeding support, and it also now supports working with the Ubuntu On Windows (Bash On Windows) implementation.
WinBtrfs is the best Btrfs driver implementation for Windows I am aware of. Those wishing to try out WinBtrfs can find the latest code via the GitHub project site.