Yes, Leopard's APIs are written to robustly support ANY app that runs on 10.3.9 or 10.4.x to provide maximum backward compatibility *provided* the apps are written inside Apple's developer guidelines. If they *aren't* then issues may arise, but you'd hope iLife was, really . Apparently Adobe had a lot of work to do to get a patch out for CS3 to make it work right with LEopard though, someone's been cutting corners methinks