For accessing volumes, both APM and GPT partitions can be used in a standard manner with Mac OS X Tiger (10.4) and higher.
Intel-based models that came with Mac OS X Tiger (10.4) or Leopard (10.5) preinstalled had to be able to boot from both APM and GPT disks due to the installation media for these universal versions of Mac OS X, which are APM partitioned in order to remain compatible with PowerPC-based systems.
Cloning an already installed OS X to an APM partition on Intel systems will remain bootable even on 2011 Intel-based Macs.
The one exception for a universal version of Mac OS X (Tiger or Leopard) is an official Apple document describing how to set up a dual bootable external APM disk for use with PowerPC and Intel.
[11] Each partition entry includes the starting sector and the size, as well as a name, a type, a position of the data area, and a possible boot code.