It is. The first thing you do is create/select an existing directory on one of the devices to sync. Then you introduce each device (via device IDs/QR codes) to each other one time so they trust each other. Lastly you share the folder with all of the trusted devices.
From there it is entirely fire n forget. The result of folders that just magically sync is not dissimilar to Dropbox.
The plus side is you pay no subscription, you have no limit to how much data you can sync aside from bandwidth and local storage on each device, and you can control oodles of settings you cannot on other more centralized clients.
No you are not. I'm using a Nexus 6 (Android) so I was unaware that there is not a native iOS client yet. There are in progress talks to build one but apparently it is a high lift to get done.
