Browsing calendars with lots of events in a day
When I've got a calendar on my iPhone with a large number of events in a single day, such as when I've imported the entire speaker schedule of a convention, then the browsing interface is very inconvenient. After viewing the events in "List" or "Month" mode, and clicking on one of them to view its details, going back to the list results in the interface jumping all the way back to the first event of the morning, where you have to scroll back down to get to other events near in time to where you were before. You have to keep doing this every time you read an individual event detail, making it very hard to browse the entire schedule.
The "Day" mode has a different interface, but its graphical presentation gets awkward if there are lots of events at the same time (which, again, happens a lot when you import entire convention schedules with multiple tracks of events).