It's lacking good support for mobile, but the mobile app is usable, and in active development. I use it daily with no issues. It mostly just lacks a no-frills setup for syncing notes on multiple devices, but they are developing a subscription for backup/sync hosted by them (I use syncthing, but others have used iCloud and google drive).

To build on the features mentioned there's also:

- A community marketplace for plugins and themes

- Simple customization and extensibility

- A builtin PDF viewer with highlighting and linking