There are a couple of reasons I am frustrated over missed calls whether with voice mail or without. One, I don't use the docked window as it can often be positioned in an area of our Windows desktop and sometimes blocks my ability to click other program window controls. Of course the dock can be moved but for someone who truly multi-tasks it soon became apparent was better to turn off this setting so to avoid it being in the way. Two, we don't have the ability to receive email notifications of missed calls.
Perhaps the Windows system tray icon could reflect not only our availability status but also any missed call count.