http://synergy2.sourceforge.net/faq.html

What's the difference between synergy and x2x, x2vnc, etc?

Unlike x2x, synergy supports any number of computers and it doesn't require X on Microsoft Windows platforms. It also has more advanced clipboard support and synchronizes screensavers. x2vnc is also limited to two computers, requires the separate vnc package, and is really only appropriate for using an X system to control a non-X system. However, the right tool for the job is whatever tool works best for you.