I've setup my machine to use cpu frequency scaling and I'm able to configure my battery to adhere to the governor as root through the Power Control module in KDE. However, when I log in as a normal user, it says ACPI power control hasn't been enabled. Are there some sort of permissions I need to set, or a group to add myself to?

Try adding the power group. I haven't looked at the dbus policies for that but it seems logical that non-root users should be able to use it.

Tried that and it didn't work. That was my initial guess, although there could be more to it.

I would look at the kernel configuration to ensure that all ACPI options are enabled.

The dbus policy does allow users in the power group to do all of the power-related functions (see /etc/dbus-1/system.d/hal.conf), and I've tried the KDE power applet as root and a mere mortal with identical results... however, this is a desktop and I have not enabled all of the ACPI options in the kernel.

KDE knows this, and gripes about it, but it gives the same complaint for root as it does for a regular user.

Sorry I can't be of more help, but do take a close look at the kernel config.