The main two new features are the new options allowing you to initiate calls directly from Google Calendar, and to open an address in Google Maps. This is a nice bit of integration between apps, and should make interacting with calendar events nicer. The update also brings suggestions for locations when you are creating and event, and a quick event creation option from the month view.
As is standard for the Google Calendar found in the Play Store, it requires a device running Android 4.0.3 or higher, so Gingerbread people need not bother. If you want the update, just head over to the Google Play Store.