With the CPU temperature for the Intel Pentium M reported by ACPI (/proc/acpi/thermal_zone/THM0/temperature) when running off AC power and idling, the average temperature with all of the Ubuntu releases were pretty close to 54C.
These power tests are just intended to be a brief look at Ubuntu's average power consumption over the past six Ubuntu releases during the past two and a half years. It is also important to note that all of these tests were done from a single Intel Centrino laptop. Depending upon your hardware, the power performance may differ. While the power efficiency is improving in Linux, it is being outweighed by more and more processes running on the Linux desktop. These tests were done from a stock configuration. If you're running Ubuntu 7.10 on a mobile device you can maximize your power efficiency through Intel's PowerTOP, eliminating extra processes, and other performance tweaks. In a future Phoronix article we may look more in-depth at maximizing your mobile Linux power performance.