NICKSLOAN  The Mac is well served for outliners, from the elaborate Circus Ponies Notebook and OmniOutliner Pro to the sleek Opal and the minimal Deep Notes. Tree is close to the minimal end, but it has a unique trick up its sleeve in “tree view”, in which all or some of the topics can extend horizontally rather than vertically. It also has all the basic outlining features plus customizable labels and background colour, but only global text styling.

There is a lot to be said for a spare and efficient outliner, but I have to agree with other reviewers that $40+ is a lot to pay, when Opal can be had for less, and Deep Notes for free. A shame, because it’s a tool that deserves to succeed, and might do well at half the price.  
(Version 1.3.2)

IG88IG88  app seems pretty nice. i like simple things like this for keeping all my notes and todo's organized. apple ical is great for a calender, but lacks any order for todo's.

so this app seems nice, it is small, and handles a lot of what omniFocus can do, BUT, 40 usd, that is super steep for this i feel.

omniFocus has a lot more aspects to it, but is twice the cost.  
(Version 1.2.7)