Simple and effective

I really like the "mini mode," which is the option of looking at either the week or month view by tapping an arrow instead of having to open an app. This allows for a smaller footprint in the today notifications while still allowing for a full view of the month, in the widget, if needed. This may seem to be trivial, but when you have a lot of widgets to scroll through the efficient use of space can decide if its a keeper or not.
On iPhone 6s Plus

the OS og about Widget Calendar