Yesterday we rolled out some bug fixes and a small improvement to smart lists.
Smart lists that specify "closed action items" can now specify items that were closed within a specific number of days before the meeting the list is in. (Previously, you could specify "closed since" with a specific prior meeting.) The "Days before" option works well with lists in meeting templates.
A typical use of this option would be to show action items closed in the past week (closed since 7 days before the meeting) in a weekly status meeting.