"Another far more disappointing thing missing in Fedora 17 is the Btrfs file system, which was originally slated as default with this release but which didn’t make the cut. You can still opt to use Btrfs during the installation process, but it won't be the default until Fedora 18."
Actually, it's worth noting that you can't easily use btrfs during installation with Fedora 17, due to an Unfortunate Concatenation Of Circumstances (I hear that's what the cool kids are calling 'bugs' these days).
We have an extensive rewrite of the anaconda (installer) UI planned. This was originally going to land in Fedora 17, but it turned out there was no way it would get done in time for that, so now it's targeted for Fedora 18. However, during the time when it was still slated for Fedora 17, the *backend* code for handling btrfs partitioning got rewritten to be much more complex and capable (it actually takes advantage of btrfs' neat capabilities, rather than just treating it as a dumb filesystem like ext4). Since the idea was that the new UI would land, the old UI partitioning code wasn't updated for the new btrfs backend code...so when we changed course and decided to stick with the old UI for F17 after all, btrfs wound up between a rock and a hard place. No-one had the time to spend considerably rewriting the old UI's partitioning code to deal with the new, complex btrfs backend handling, so we just disabled btrfs as an available filesystem during interactive install of F17.
You can still use btrfs for partitions when installing F17, but only if you do a kickstart (scripted) install. You can't do it during an interactive install. It'll be back, along with the UI rewrite, in F18.
This is all mentioned in the release notes, but of course El Reg readers and journalists are far too cool to read documentation. ;)