Recs.
Updated
Org-mode is a note taking tool to be used with Emacs. It is geared towards authoring documents, taking note, keeping todo lists and planning projects, all in a simple text format.
Specs
Pros
Pro Versioning can be tracked and synced using Git or other VCS
Org files are plain text, and lend themselves well to version control. Emacs also has good integrations for various VCS.
Pro Basic spreadsheet functionality
Org-mode has some basic spreadsheet functionality. Other than auto-formatting ASCII tables (a notoriously annoying problem), it also has support for LISP-like syntax to define equations or any other functionality that can be achieved through spreadsheets.
Cons
Con Difficult to learn
Org-mode has a difficult learning curve since you have to learn all the keybindings and commands. It's especially difficult if you are not used to Emacs.
Recommendations
Comments
Out of Date Pros + Cons
Con Tied to machines with Emacs
The app is not all that portable. For example, if the user wants to take notes or make to-do lists while out and about, that is going to be difficult unless they have a machine with Emacs installed on it with them. Basically, Org-mode has little portability in comparison to other note-taking apps that have clients for mobile devices.