If Windows 7 increases power consumption then it would stand to reason that this would increase the number of cycles the battery experiences in a given time frame, worse yet, the lower the charge an LiIon/LiPolymer experiences the less ability it has to recharge. To me it sounds like a consequence of increased power consumption and the performance profile of Li batteries rather than Windows 7 doing something specific to "kill" a battery. I'd be willing to bet that using the same amount of power on any other OS would cause the same effects.<p>[edit]
For clarification I mean to say something along the lines of draining an Li battery to 80% 5 times is better than draining it to 0% once. (Note: There is still lots of charge left in an Li battery at "0%", if you get it to actual 0V the battery is permanently dead and cannot be recharged)