This is a great productivity tool to use to keep track of your life and thoughts! I just discovered this a couple days ago and already love it! If youre looking for a sort of "notebook" you can keep on your phone for ALL your todo lists, thoughts, journals, project outlines, etc etc, this is the app/service for you!
I took a small amount of time to watch their YouTube videos to understand what is going on. While they are lacking documentation within the app/site itself, they do seem to have documentation available if you just use google.
I will say though that the app version versus the website version is far behind in terms of features. It is difficult to copy and paste (or not possible, I still havent figured it out) lists and sub lists currently, there are no menus that pop up over the bullets like desktop website has, no shortcut keys or options in app ver, and probably more. Also no ability to add pictures is a bummer, but you could upload them to a "cloud" and just paste a link to it instead I guess. So -1 star for these problems. None of those are necessary to get started and make it useful.
Otherwise if you use it in conjunction with the desktop website version it syncs automatically so you can do your hardcore editing there and minor updating and reference on your phone. I can already feel it changing my life. I have always wanted to be able to refer to any notes or to do lists from anywhere I am in the world, rather than scattered or forgotten in my house never to be seen again.