Schedule Power Off

I often recommend that offices leave their computers on at night but lock them for security so that backups and updates can be scheduled to occur overnight when they won't impact work during the day.

A friend asked yesterday about putting a timer on a computer so that when the backup / update is done it could power off.  While at first glance that didn't seem like a good idea it quickly led to the thought of scheduling a power down or hibernation.

A quick google search pulled up a number of utilities for doing this.  Wondering if anyone out there is doing this? My immediate (haven't thought this through) list of requirements includes:

*  Ability to administer centrally
*  Ability to Hibernate or Standby rather than power off completely.
*  Sensitivity to someone working late -- can't ignore the user.
*  Ability to setup a variable schedule to accommodate different things on different days of the week.

There may be more, but the above would be ideal.

Any thoughts?