When I first upgraded to Mavericks Synergy worked fine. Recently I started noticing a lag issue, cursor movements and typing was delayed sometimes, othertimes it would become unresponsive with Synergy Client running on my Mac. I rebooted and left the Log window open and found constant disconnects, it would alway reconnect but it would drop the connection and the cursor would jump back to the Server.
I found a work around that makes it mostly usable again. I went in to my Applications folder and opened Get Info on the Synergy.app and checked the 'Prevent App Nap' box. Much more responsive now.