I wanted to replace rsync for my current host backups.
I had 2 hosts (1 laptop and 1 desktop) that would get there changes polled from a backup server. (polled = cronjob ran every hours) Ofcourse those boxes are not always on and a frenzy of cron mails happen every now and then.
I replaced everything with syncthing, they have clients available for linux, illumos, openbsd and mac. With the config below (client::folder master = yes, server::folder master = no) we prevent the server from accidentally overriding a file on the client. The client knows the server's IPv4 and/or IPv6 address so we do not need global or local discovery nor UPnP.