My main issue with the calendar is let's say you have your settings to display the start of a day as 8 am and the end of the day at 5 pm.
If you have an appt at 7 pm on a particular day you don't see that appt. unless you scroll down to check. So I often don't see appts. as I'm scrolling through the days in the day view. Very frustrating.
* My old Palm would adjust the day if you scheduled a later appt. In this example it would automatically extend that day to 7 pm so when you were on that day you would see the later appt.
I dont have a suggestion for a different app. but have you tried agenda mode? it shows all appointments in a day in a neat list, and there is no way to miss one because the day ends to early.