Item recurrence management (for tasks, etc.)
Task management is central to any PIM.
Most features related to "tasks magement " are possible in IQ.
But there is one very important aspect to be added : recurrence management.
FYI, In Mantis this is - http://mantis.sqlnotes.net/view.php?id=836.
Also, MyLifeOrganized is a good place to look at how recurrence can be supported well.