I mostly use the todo-list for items that have multiple "sub-parts". It could be 5, 7, 13, 17, 24 - nearly any number between 2 and 25. What I think could be useful, both for me and many others, is a field in the "new task" window that allows to enter how many "sub-parts" the item has. And then, if the subparts-field is activated, the "in progress"-menu will allow select how many parts that are done directly, and the progress bar percentage are calculated. Let's say I have an item with 7 subparts, then the "in progress"-menu would say "0/7, 1/7, 2/7, and so on", instead of 0%, 10%, and so on.
What do you think about this?