With the upgrade to the 3.8 kernel, power consumption on a Dell XPS 14 resulted in an increase of a 50% (and more) when running on battery. With 3.7, I observed (powertop, all tunings set to "Good") a power usage as low as 8W. With kernel 3.8 I'm not able to get any lower than 14W (and I can hear the fan is always running, while with 3.7 it didn't happen). Booting with 3.7 restores the good behaviour. Powertop output looks the same, so I haven't been able to pinpoint the problem more exactly.
Created attachment 705231 [details] Dmesg 3.7
Created attachment 705232 [details] Dmesg 3.8
If you're still seeing this with 3.8.7, can you please use powertop on both the 3.7 and 3.8 kernels to see if there is a particular device that is causing significantly more wakeups, etc? There is a known i915 issue with resets in bug 866212 but it's hard to tell if you are seeing that or something else.
This bug is being closed with INSUFFICIENT_DATA as there has not been a response in 2 weeks. If you are still experiencing this issue, please reopen and attach the relevant data from the latest kernel you are running and any data that might have been requested previously.