For those who have been waiting for Btrfs on the next Fedora, get ready to dissapointed since it will NOT be included in Fedora 16 and likely will be postponed until Fedora 17. This is an official announcent made by Josef Bacik to development mailing list of Fedora about Btrfs status.
I think it's a good decision as making a certain filesystem to be the default filesystem used in a distribution is not an easy task and it requires lots of testing and standards compliance. So far, Btrfs has shown us a great progress, but still can't made it into Fedora 16.
We shall wait for future releases of Fedora that will likely to include Btrfs as it matures on each release of Linux Kernel cycle