Narrowing down to one feature is tough.  But most recently, we have implemented the use of spreadsheets for data gathering for SEC and management reporting with our global subsidiaries. The templates were easy to set set up in spreadsheets and Workiva makes it easy for our subsidiary accounting teams to use; we are saving so much time.  Added to this, using the spreadsheet formula in the templates for child / parent references makes it so easy to consolidate the data.