The Fedora project has backed off of its goal to run on Btrfs by default in the F16 release. "Fesco outlined basic requirements that needed to be met by Alpha for the switch to be allowed to happen and we have not met those requirements so it won't be happening for F16." Among other things, those requirements include a working filesystem checker, and that is not yet on offer.
August 8, 2011
No Btrfs by Default in Fedora 16
Read more at LWN