The tooltip for the "Monitor Power Management Control" checkbox says "Disable Display Power Management Signaling". This is very confusing. I would think that "Display Power Management Signaling" is required for "Power Management Control". So I I want power management for my monitor, should the checkbox be checked (because I want Monitor Power Management) or unchecked (because I do not want to disable DPMS)?
With the redesign of the settings-dialog, this has been dealt with. The option is now called "Handle display power management" and is put close to the DPMS stuff so it's fairly self-explanatory.