I upgraded my mini laptop to natty today, and because of all the commotion about the extra energy consumption I opened powertop.
Indeed the power seems to be higher, looking at the active task list, the kernel IPI was waking up the cpu 600 times a second. These ‘wakeups’ turned out to be caused by conky. Closing conky, stopped the wakeups. (reducing the total to 20-30 a second, still high-ish, but ok) and made the power usage drop from 12.8Wh->10.3Wh.
This is similar as before. The temperature off the cpu dropped a little.

specs:
CPU: AMD Athlon II NEO K-345 (2 core, 1.4GHz)
Memory: 6GB ddr3
Battery: 90Wh
Screen: 11.6″ 1366×768 screen (led)
Disk: 250 gb sata disk.
Other: SD Card reader.
Interconnect: WIFI N + Bleutooth 3, 100mbit ether, hdmi, dsub
Other: build-in webcam.