Syncing music. Contacts. Calendars. Safari Bookmarks. Notes. Apps. Ringtones. Videos. Photos.
The killer feature of the Apple ecosystem was the way the Digital Hub worked together. It's all gone by now. They demand always-on Internet to connect to the cloud.
I'm trying to rewrite my own ecosystem one app at a time (I've done Notes and Maps, halfway through contacts & calendars, and still need to start music & photos). It's going to take years of on-and-off work, but I don't trust Apple to keep providing that, so I must make my own. Some shell scripts linking other apps just won't cut it for me - I want a scriptable, syncing ecosystem that Just Works.