I use org-mode for emacs and it's great, but if you're not already using emacs I wouldn't recommend learning it just for org-mode.
Seconding org-mode, with the suggestion of Spacemacs to minimize the barrier of entry into emacs. org is awesome for anything you could want to do with text; lists, tables, calendars, project management, word processing, you name it. If there's something you want to do with your text, it's possible to do with org, and if the functionality doesn't exist yet anyone (who can program) can extend it and add the functionality. It's incredibly easy to work with the output as well, I know of people who publish ebooks straight from their org output. As a bonus, it's free in every sense of the word. The only downside is getting started. If you aren't familiar with keyboard based navigation or vim style motions if using Spacemacs / evil-mode you'll feel like you're stuck and have no idea how to use this text editor from '85. It feels incredibly unintuitive until it doesn't. If you edit text daily, however, it's absolutely worth it.
Emacs is, according to popular joke, an operating system with text editor function :P. Seriously though, Emacs is an extensible with hundreds (if not thousands) of add-ons programmable text editor. Programmable means that you can automate quite a lot of work from within it. Really good for programmers, not sure if worth to use just for notes. Org-mode is an engine that depending on some instructions from you takes the body of the note and applies the syntactic/formatting rules to print it. What's cool is the fact it's a rather easy syntax that can be exported into a lot of formats (HTML, LaTeX, Markdown, RTF etc).
I know quite a few people in the emacs community picked up emacs because they started using org-mode. I think normally someone else tells them how they organise everything using prg-mode - projects tracking and management, schedules, calendars, to-do lists even documenting their emacs config files. Emacs is definitely a committment though.