unison

unison (no, not the news reader) has replaced rsync and ssync as my synchronization tool of choice.

• Runs on Mac OS X, Windows/Cygwin and Linux
• Is fast and efficient over SSH
• Has an interactive command mode for CLI use
• It has a Cocoa GUI

• It is written in Objective Caml
• It installs badly (you’re better off just dropping it in /bin/unison)
• If you don’t put it in /bin/unison, it isn’t smart enough to find its peer using $PATH over SSH
• It is incompatible between versions