The calendar is my least favorite update in the new iOS. The month overview does not give you enough information. I miss the color-coded of what was going on for each day of my calendar. The Day view takes up too much of the screen. It almost doesn't seem as clean as the rest of the iOS 7 design. It's the one app I've heard from most of my friends that they don't like the new calendar and I'm also hearing it from my mother and her friends.
Apple, the calendar needs your attention.
Apple, the calendar needs your attention.