Timely Feedback To Users While Loading Information

You want to book an appointment. You add potential list of attendees. Their availability is not shown instantly. You wait, and wait, and wait. 

MS Outlook 2013 changes that. While you wait, a message, We're checking everyone's calendars is displayed.

Products must be forgiving when 1)Users make mistakes and 2)Products make mistakes. 

MS Outlook does it. How about you?