I was surprised to learn that with the initramfs system that root filesystem flags need to be passed in as kernel flags. I'm wondering on bug 537882 if that can be made better.
In the meantime, I added this to the yum upgrade page in the wiki:
# If your root filesystem does not mount with 'defaults' options, you will need to add the root filesystem's mount options to grub.conf with the kernel flag rootflags - initramfs does not pick up the options the way initrd used to. e.g. if you mount your root with the flags data=journal,relatime then you would add to the end of the 'kernel' line in grub.conf: rootflags=data=journal,relatime .
If it makes sense for this to be on one of the other notes pages (I first looked at relnotes and common bugs before filing a bug where Harald Hoyer helped me out) then please make it so.
-Bill