OK, I too have had issues. But after some investigating I found the root cause for the syncing issues between the iPhone, iPad, and iCal on my Mac.
The reason people are having issues is due to a mis-match of "calendar type" slected when one makes a calendar entry and not having all the calendar types selected to show on each device. Let me illustrate this point by images and ellaboration.
A calendar event must be associated to one of three calendar choices on the iCloud calendar type - Home, Work, or Calendar. Also, if you use a calendar type to make an entry then you must have that type selected to show on all devices. Otherwise it will show on those that have it enabled and not on device that don't have it enabled.
I have created four test events to illustrate this point. Test 1, 2, and 3 are events associated to one of three iCloud calendar type. While the "Introduction" event was entered using a non iCloud calendar type - "Work".
You can see Test 1,2 & 3 calendar events showing on all devices. However the "Introduction" calendar event only shows up on the iCal.
All four calendar events as seen on iCal on my Mac Pro. The event "Introduction" was created in iCal on the Mac Pro. This event was set to My Mac Work Calendar which is not a choice under iCloud calendar options. This is why it only apears on the Mac Pro and not the other portable devices.
iPhone: Only three events showing
Test 1 event was entered in iCloud Home calendar on the iPhone
This screen shows that all three iCloud calendars have been selected to display on the iPhone. This is why you can see all three Test events on all three devices.
iPad: Only three events showing
Therefore, when you make a calendar entry on any device and you want it to show on all three devices make sure you select one of three iCloud calendar types. Otherwise it will only show on the device you enter the event.
Hope this helps...