Btrfs

What is the most powerful feature of Btrfs for you?

Copy-on-write? Instant snapshots? Transactions? Deduplication:

duperemove /var/chroot/ /usr/ /bin/ /etc/ /lib* /var/lib/ /opt/ /boot/ /sbin/ /home/ -rd

Kernel processed data (excludes target files): 56513581056 Comparison of extent info shows a net change in shared extents of: 19615367505

Cool economy on chroots huh? And I had only four chroots for that moment! I guess this gives new wide ranges for VPS and VDS hosting providers. But who of them uses Btrfs...