Hi :)
Good news and bad news about multi-booting with grub!
The good news is that grub almost invariably finds the presence of any other OSes on the machine and automatically adds a line to the boot-menu to allow people to choose which OS to boot in to. Failing that it is possible to edit grub to include them.
The bad news is that grub2 developers have found that there is a problem booting into EFI systems at all. You might find it worth joining the grub2 developers mailing list to help them test work-arounds and alpha versions of patches.
http://lists.gnu.org/mailman/listinfo/grub-develGood luck and regards from
Tom :)