I wrote the F18 Alpha RC3 netinst ISO to an actual DVD, and booted it native UEFI. It gets through grub fine, to dracut, but anaconda fails to start. I see a couple of messages: dracut-initqueue[381]: Warning: Could not boot. (repeated x1) dracut-initqueue[381]: Warning: /dev/root does not exist and it dumps me to emergency mode. Not sure if this is dracut or lorax or pungi or what the heck ever, just assigning to anaconda for now as I know the right people will see it.
Also affects DVD, not surprisingly.
*** This bug has been marked as a duplicate of bug 855849 ***