Anyone know how the upgrade certs work yet?

Are the regional certs only valid within the regions (e.g. only within Central America; flights to/from US require global certs)? Do you have to use 1 cert per person you want to upgrade, or is it 1 cert per reservation? 1 cert per segment or origin-destination pair?

Their English FAQ is extremely light on details. Anyone light that can be shed is much appreciated.