Using the latest Rawhide live cd, it does KMS at the boot process, and then stops. If I remove "quiet rhgb" from the GRUB kernel parameter I can see it is because it have found my LUKS encrypted /home partition and asks for a passphrase. If I leave "quiet rhgb" and add "nomodesetting" almost the same happens. Here here I see the loader bar at the buttom for less than a second, but still the curser it just the top left corner, if no information that it waits for a LUKS passphrase.
*** This bug has been marked as a duplicate of bug 527426 ***