Usually my thoght process goes from general idea to multiple sub-ideas until I get to doable tasks. No other app that I've tried allows you to do this the way Workflowy does. They all let you group by tag, or notebooks or whatever but they are usually one level grups.
The ability to nest list inside other list items is it's sell point to me. Dividing thoghts into more specific sub-tasks is key for me.
The way to interact with each item is a bit hard although key shortcuts are amazing.