Does unison still have the problem that it refuses to work unless the exact same version of the program is installed on every computer? Also, I've found it extremely hard to install on linux boxes where I do not have root access.
Fortunately, installing unison can be done quite easily without root access. On my synology, I simply downloaded the arch linux arm packages and extracted the 2.48.3 binaries from there. Because the packages in Ubuntu 14.04 are outdated, I extracted the binaries from the arm linux x86_64 packages for my laptops. For MacOS, there are downloadable 2.48 binaries that also work out of the box.