I have been fighting with this, hopefully someone else who has a Dell can compare and see if they are having the same issue.
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq yields that my processer is running at 600 MHz, less than half of its 1.5 MHz potential all while plugged in to A/C power.
An echo 150000 > scaling_setspeed in this directory will bump it up to max 1.5 MHz (or so it says) but low and behold 1 minute later its right back down to 600 again.
ACPI is on and running, suspend to ram works and so does my battery applet in the Gnome panel.