I built my own Macintosh clone, and chose a motherboard
with EFI (these are still hard to find), and here's an
interesting question.
It has a BIOS module preinstalled onto the board, and
allows me to chose how to boot an OS, either with EFI or
BIOS, even if the OS supports EFI.
So, with Mac OS X, with BIOS boot, it takes 59 seconds.
With EFI boot, it takes only 32 seconds.
With 2003 boot, it takes 64 seconds with BIOS boot, and
45 seconds with EFI boot.
What part of EFI allows this rapid boot processes? I notice
with EFI, there's much less HD activity during boot too...