Well, I should try it, where should I ask and donate to get it booting in EFI machines? 
Just ask on aros-exec.org

If I wasn't so bogged down in iPhone code, I'd try and have a look myself!
Michal did say that the EFI actually provides all the services that AROS currently relies on GRUB to provide... So if might just be a case of building an AROS build that uses the EFI to load the exec.library etc...
-Edit- hmmm, did a bit if checking, and it looks like GRUB2 is in use by Ubuntu now... That might be a quicker and simpler way to go!