The behavior of Synergy is similar to having multiple monitors on a single computer with the added advantage that you’re controlling multiple systems. Since I have both a Mac OSX desktop and a Windows laptop on my desk it was nice to reduce myself to one keyboard and mouse! Even clipboard data is shared between the systems.
Setup was a little less than intuitive but well worth it. Out of the box, security is fairly weak, however the Synergy project page does have instructions on how to tunnel Synergy traffic through SSH. Mac, Windows and Linux binaries are available along with the source code for those DIYers.