Custom fields are amazing and our team uses them extensively. However, we feel like we have to hack the system a bit to add custom fields to subtasks.
Since custom fields are tied to a project, we have to add each individual subtasks to a project in order to add custom fields to that subtask. This seems silly if the parent task is already added to a project with custom fields.
It would be nice if, on a project level, we were able to specify if the custom fields should propagate to subtasks or not.