said by kitsune:There is also a settings button where you can elect to automatically sync any new content when it's added.
From the Apple KB article you linked to:
Previously downloaded or non-iTunes Store content can only be manually transferred. It may be necessary to authorize iTunes Store content for playback on other computers.
Given that it only does iTunes Store content, which can already be automatically downloaded via iTunes in the Cloud without requiring a LAN connection between machines, the syncing functionality of Home Sharing is crappy, IMO.
said by intok:Why can't they just detect each other via bluetooth or 802.11* like when you create a network?
The automatic action APIs for computers in the same proximity that Yosemite is adding may enable what you are doing. But Apple has always been reluctant to help you get non-iTunes store content from computer to computer.