The RFC for iCal supports up to a recurrence at the second level.  While I think that is too much, you should be supporting recurrence at the minute level.

The Windows Task Scheduler supports this, as well as Linux/Unix Cron.

If you are using the Scheduler Widget as a UI for a job/task scheduling system, then having the ability to schedule at the minute level is important.

This is related to the feedback request to "Add hourly recurrence editor to Scheduler".

Having the ability to setup a recurrence outside of the scheduler would be nice.  The ability to use recurrences for other things that don't make sense showing up on a scheduler.  An example would be setting up a an email subscription.  I want it to recur, but I don't need to see it on a calendar.