We made a small UI improvement that makes it easier now for you to see how many Checklist items (subtasks) remain open on a card:

A number will appear next to the Checklist icon when you are looking at tasks on a board: this is the number of open Checklist items for that task. We don’t show the total number because it’s the remaining ones that are more important, but if you hover over the number a tooltip will show you that as well: