Update to previous post: I downloaded and installed the Linux ATI video driver for my Lenovo T400. Immediately my battery life doubled. I am now seeing battery life roughly comparable to Windows 7 – approximately three hours. Additionally, the heat generated by the computer is much lower than with the old driver. Apparently, the video GPU was just cranked up to 100% all the time.
If you use Ubuntu on a notebook, and are suffering poor battery life, a good place to start is with your drivers. Who would have guessed a video driver would make THAT great a difference?