Comment about stability
RAID-1 or RAID-5?
"3 1TB disks in an md based raid1 yields a /dev/md0 with 1TB free space and the ability to safely loose 2 disks without losing data. 3 1TB disks in a btrfs volume with data=raid1 will allow the storage of approximately 1.5TB of data before reporting full. Only 1 disk can safely be lost without losing data."
That sounds more like some kind of weird, inefficient RAID-5 arrangement than RAID-1. I don't know btrfs enough to say it's wrong, but I know RAID-1 enough to question it?
btrfs with fsck hook and fstab pass
Apparently one does not need to have a btrfs partition fscked on boot, so there should be a '0' for 'pass' in the fstab for any btrfs partion. I had relatively slow boot ups with a pass of '1' (btrfs was root)
the genfstab script puts a '1' in for 'pass' by default