I like the fact that there's a little competition.

Personally, I tried btrfs as a root filesystem for a couple years. It definitely had weird gotchas like running out of inode space pretty frequently when making use of snapshots. A few years back I also ran into a problem with a bunch of zero length files (race between writing metadata and content?)

I switched this year and I found zfs to much more user friendly and reliable, although setting up zfs on a root on ubuntu is still a manual process.