Microsoft's Nick White is joining in on the battery conversation, admitting what we all know to be true, that Aero is indeed affecting battery life. Although, the percentages he quotes seem a little low IMO, it does appear we are starting to get somewhere.

Nick also offers up this nice little p.s. in regards to testing software for battery impacting:

As an aside, I recently learned that testing the impact of software features on battery life is exceptionally tricky, even by benchmarking standards.  A huge number of variables must be controlled for.  In fact, something as simple as the way a battery is handled can introduce enough variability into testing to make it difficult to identify the true cause of any observed changes in performance or battery life.  This is because the charge a battery requires can vary considerably based on, among other things, the battery technology (Li-poly, Li-ion, Ni-MH, etc.), how recently the battery was power-cycled, how old the battery is, and even the temperature of the battery when it was charged.  Wow.

Along those lines, James Kendrick just pointed to a nifty little app written by Tamir Khason, a contractor working for Microsoft. It is called Vista Battery Saver, and it automatically turns off Aero ( not just transparency ) and the Sidebar while the mobile device is on battery. Tamir claims that the program will save up to 70% of your battery by disabling those battery hungry Vista features.

The current version is beta 1 and it would be good for everyone to let Tamir know about bugs. Until some permanent fixes are in place with Vista, I'd consider this little app a "must have" in the mobile pc software kit.

Question - shouldn't we encourage Microsoft to implement this into their Mobility Power Settings? Turning off Aero and Sidebar should be fairly easy to do if they are already turning off transparency.