It’s honestly been a while since I’ve actively explored iTunes or tried to solve syncing media in the house so this feature may have existed for a bit. Tonight however, I was setting up a new machine and activated home sharing and then clicked into the settings (bottom right in iTunes from within home sharing).
As you can see there’s a handy option to automatically transfer new purchases between machines … While I wouldn’t want to have my full collection floating around on multiple devices based on the size, it is nice to have the option to capture the updates. I just purchased the new Alexander album on my main machine and I can see each track is syncing over as the initial download completes. Very cool.