Battery life has been really good with the Lenovo X61T Tablet PC I’ve been using. I’m getting about 6 hours with WiFi on with an 8 cell battery.
To get that, I set my power plan to Power Saver. Then, I modified the Power Saver Advanced Settings to have better performance when plugged in: set the processor to a min of 75%, max of 100%. I also adjusted the screen brightness for plugged in value, too. Screen brightness on Power Saver under battery is set to 40%. I’ve also got the Sidebar and Aero turned off. Using the standard Thinkpad Default power settings, I was getting between 3 and 4 hours. That’s pretty good battery life if I say so myself!