We have several executives who have Admins managing their calendars for them. When the executives add calendar entries themselves, it can take hours for those items to show up in the view their Admins see.
Admins have "Editor" rights in Outlook 2010.
We have Exg 2010 in a two server cluster scenario.
New items are a mix of items added in Outlook by the Exec or on his/her smart phone.