I don’t know if I’m pointing out something everyone already knows, but one of the features of Aperture 3 that I really like is the ability to run it on my two machines at the same time, using the same license, on the same network. In previous versions, when Aperture was launched, it would detect that the same serial number was already in use on another machine on the network, flash you a dialog box alerting you to this, and quit immediately.