I'm running KM on three Macs, and I love how flawlessly syncing of macros works. But when I add an action to Favorites on one machine, that isn't reflected on the others. I'd love an option in preferences to sync favorite actions, as well. 
Currently only things in the Keyboard Maestro Macros.plist file are synced between Macs. It is possible this will be extended in the future, but not in the short term.