Revision 1 doesn't have EFI included, so you most likely haven't installed it, unless you followed a Guide to do so!!

Rev.2, which is not yet released to public, is meant to be installed as GUID + EFI, I guess.

EFI is not a must, but it's an improvement for the system.

Better Performance and stability because of apple stock kexts, everything runs very smooth, working system updater etc.

Actually without EFI I had nice system performance, but with EFI it's just as smooth as a real Mac.