my main issue is that btrfs is advanced and we have much to think about the way we want to include it. rollback support and friends are very cool (this just saved me the other day actually) and i think would provide a great benefit to the arch rolling model.
additionally its not as simple as other FS's. the subvolume/pooling aspect of btrfs means that if you wanted your /var to be compressed, your /home to be (insert mount options), and your root to be (insert mount options), all RAID10 across 4 devices... you would mkfs.btrfs ONCE, then create individual subvols for each. methinks w/o looking at AIF code that this is rather exotic compared to the partition-per-FS options currently available. i just think it's a good idea to start thinking about and integrating all of this now, as btrfs is evolving rapidly and there is a tremendous amount of community interest in it across all distros. btrfs was merged at .29, declared ready for early adopters in .32, and gaining interesting features + stability all the time. i believe it will be "declared stable" sooner than some may think. and rollback is super useful, and would be a natural addition to the Arch's rolling model... afiak the Fedora 13 rollback is mostly useless; the hook i have created is more featureful, which makes Arch the only distro truly supporting btrfs rollbacks :-) (not OOTB however...) C Anthony