Good news :)
With syslinux-6.01-pre5 all things tested seems to work! Finally!
cdrom (ISOLINUX): OK disk (SYSLINUX [VFAT]): OK disk (SYSLINUX [EXT4]): OK disk (ISOHYBRID-MBR): OK network (PXELINUX): OK
Also tested, all other menu items, reboot, hdt, memtest, etc...
Tests was made under qemu-1.5.1.
PS: Since syslinux 6 supports EFI, maybe in a future (2013.08 or 2013.09), if all things work, I am going to replace gummiboot with syslinux.