The paid version even comes with Android App Support - the 'killer feature' that allows a Sailfish device to run full Android apps in a sandbox (https://jolla.com/appsupport).
Some people will inevitably moan that it's proprietary, but that's just the UI layer; the rest is wide open, familiar Linux. I can SSH into my device without any fancy workarounds, and it works almost identically to a desktop machine.
(Besides, how else is a company meant to survive in the super-competitive mobile device market? The OS is cheap. Android App Support is awesome. Pay up and be grateful!)
The UX is simple and consistent, WAY superior to iOS and Android.
Most importantly, it has an ecosystem: the Jolla app store, a comprehensive SDK, and an alternative open source app repository (https://openrepos.net/).