It is kind of interesting that it appears XFS will be the default filesystem in RHEL7?!?! Until recent fixes in RHEL6.3 and on, there were many many problems with XFS on RHEL6. Even now, things are not good for the situation of having a filesystem with many small files.
I would assume RedHat knows what it is doing by making this change, but geez, I hope it actually works!
For a taste of XFS fun in RHEL6, see this
I assume redhat is testing RHEL7 with an XFS filesystem that has a billion files on it!?!?