Does it have Optimus, i.e. two graphics chips? Which chip do you use more often? I keep my T410 exclusively running on the power-hungry nVidia chip and don't get more than 2hrs of battery life.
I'm running the nVidia chip exclusively, but when I get around to it, I'll probably switch, as I'm running an openbox desktop that just doesn't need that kind of graphics acceleration. I have yet to figure out a painless way of switching between the two, but that's probably because I haven't really worked on it much.
I have only ATI cards and the difference between open source driver and proprietary driver is world apart. With radeon I have +2 hours, with fglrx it's ~4 hours.