The current Windows calendar app does not integrate well if you have an Android device and use Microsoft Outlook for e-mail and managing your appointments. Since the default calendar on Android phones is the Google calendar and there seems to be no way to make the Outlook calendar the default, this requires you to manage appointments in two different calendars. An integration where the two synch together would be great.

Of course, maybe I just don't know how to configure it all correctly to make this work :-)