But absolutely 100% remember to block automatic updates because even minor-minor version updates change the protocol (and even different versions of the ocaml compiler with the same version of unison source can mismatch.)

This pain has always stopped me using Unison whenever I give it another go (and it's been like this since, what, 2005? with no sign of them stabilising the protocol over major versions.)

The recent updates have stabilised things a while lot with nice features like atomic updates.