Appointment item icon to indicate whether required meeting participants accepted when looking at multi-day, week, or month view
How often do we join a meeting only to find out not all the required attendees accepted? "Let me see if XX accepted...oops, looks like no response. I will try to ping him/her, otherwise we reschedule."
With full calendars, no one is going to sit there and check them one at a time on a daily basis. This could easily be solved by a simple icon on the appointment item "pill" indicating whether the meeting is "viable" or not. A user could then take action, like prompting required attendees or rescheduling.