There have been several cases where there has been a subtle point of friction for me in the UX. Some of these times i don’t even fully realize that something is annoying me. (i.e adding a subtask)… until you fix it and make it awesome. the little ‘add sub task’ button is such a small change but when I use it now i remember how slightly annoying adding a task was before and it makes me happy. 
Your attention to the little details is why using this product is such a breeze. Keep up the great work.
keep up the work Asana!