One thing i’d find helpful is the ability to reorder items in a checklist. As a previous Things convert, I liked being able to manage priority of the the incomplete items by dragging the most important items up top within the list as priorities changed.
As others have said before…it would make a huge difference being able to easily search by unchecked items. Right now I’m tagging items and having to search by those tags to see what’s still outstanding, checking them to be done, and deleting the tag. I prefer using the checklist than a tag alone to differentiate open items, but right now it’s just creating more work.