There is a new outliner for OSX (introduced on July 24, 2014). It is called Outlineedit and sells for $18.99 at the AppStore, that is, it's not cheap. "Works like you expect it to: set an outline title, create new items, then structure them using indentation and drag & drop." It also has a search function, can create color labels, has a notes function, allows checkboxes, can print and create PDFs based on an outline and can copy highlighted information from a web browser into an outline.
It is certainly an interesting application and worth a look. Whether it is worth $19.99 is a different question.