I use Keep, and it's become a pretty central part of my life over the last year or so. I never stuck with any other to-do apps- either they were way too extensive (Evernote) or not flexible enough (Wanderlist, Google tasks, Any.do, etc). I like Keep because it lets me store random notes that I need access to during the year (books I want to read, workout lists), to do lists that are transient (a shopping list, recipes), and to do lists that need to stick around for a while (Personal Goals for September). Something about having all that just displayed on one scrollable screen works really well with my mindset where other apps feel tedious and unhelpful.