gnome-power-manager interface confusing (and undocumented)

[DaveAbrahams]

Binary package hint: gnome-power-manager

I know there are at least several levels of display sleep (available through xset) and the interface doesn't tell me which one(s) I'm going to get. Is this the full power saving I really want, or some intermediate state, or what? Also, the "Set display brightness to:" sliders have an unclear effect. Just when does that brightness setting take place? Is it part of g-p-m's notion of "display sleep?" What does "Dim display when idle" do exactly? How long does the computer have to be idle before dimming begins? Is the display supposed to undim when I start using the computer again?

The answers to at least some of these questions should be self-evident from looking at the UI, but they are not.

This is in Ubuntu Intrepid 8.10

gnome-power-manager:
  Installed: 2.24.0-0ubuntu8.1

Please see also https://bugs.launchpad.net/bugs/308815 and https://bugs.launchpad.net/ubuntu-doc/+bug/310831
Also, note that http://www.shallowsky.com/linux/x-screen-blanking.html makes a credible claim that screen power management should be handled by screensavers.