very nice idea; I've used Workflowy for a long time for todo-lists and keeping my "done" list is something I have to do manually as a workaround there. Having just played with donel.ist I can confirm it's quite compelling, satisfying and rewarding to note everything I've completed today, definite dopamine hit. I'd suggest you automatically colour new tags differently, and the UX for adding a new tag is a teeny bit clunky - you have to create the tag and then apply it. Also it might be nice to have the ability to add tags to an item just by typing "#work" into the main text entry box.