I am using syncthing to sync my PC files. I'll add synching into the software bundle some day, it is cool.

My own core requirement is backing up iOS.

Whole-device backup is cool when you want to.

1. setup a new device as same as old ( backed up ) one.

2. prevent from you forgetting to put your important files in syncing folders.

3. even some commercial backup solution can boot up a system via a backup.