How I do it, I send the same command to multiple ip addresses.
Unless you connect an x10 receiver plus software to each thick/thin client, you need PowerHome or any other HA aware software to tell each instance of XLobby of a status change.
You have PH tell 1 XLobby installation, and then have that XLobby tell the other installations to change status (not sure what the delay would be.)
Network bandwidth still an issue but load cut down on PH.
What would be cool is if PH were to broadcast via UDP (no specific address) and tell any listening devices of a status change, kind of how x10 works, where x10 receivers can hear all x10 commands as long as the house code is set properly. (Some receivers can hear all commands regardless of house code settings.)
I love XLobby, but not sure what the future holds, for us using PH as well.
Check out http://www.ehomecreations.com/
as the developer is designing a gui front eend from scratch with built in PH integration.