Among other things,
a poem. 
But seriously, the biggest problem you would have with getting OS X to run on non-Apple hardware is, as you already mentioned, the fact that no Wintel manufacturer ships a machine with EFI, and won't until at
LEAST 2009, when Blackcomb is slated for release. (Keep in mind that Vista was originally slated for release in 2003.
)
That of course is assuming that Blackcomb uses EFI, which is by no means a lock. Vista originally used EFI, and that was scrapped, along with just about every other feature that made Vista worth buying.
It is of course possible to modify/crack OS X to do this: but even if you did, Apple's legion of lawyers would be all over it.