Its easy to DOS the BTRFS and kill the system. A normal user can do it. Just create a couple of big files. Then, copy a large number of small files. You will get ENOSPC at around 90%. Then, delete the large files. Even with most of the space being free, it won't allow you to create new files. All new requests will get ENOSPC. Bug is at: https://bugzilla.kernel.org/show_bug.cgi?id=16508 BTRFS is a mess. Go read their mailing lists.

If you look at the photo closely, it says "Enhanced Write Performance" and "Encryption" as the new features. So, I would think that's an indicator of good things to come. The read speed and random IO speed was already very good with x25-m.