from a letter to the Inquirer from Nik:
I want to bring to your attention a terrible problem that afflicts all notebooks with PCI Express graphics cards and the Intel 915 chipset: They consume about 5W more than comparable notebooks with Intel 855 and AGP and / or newer 915 based chipsets with integrated graphics. So a 915 based notebook (like my 4600) with X600 graphics card uses 22W on average, whereas the older 855 based ones with ATI 9700 use 17W or less. On average. Thus, the battery life is much worse of the newer notebooks. My new TravelMate 4600 lasts 2.5 hours max, whereas my old TM 803 easily makes it past 4 hours. Joerg Wirtgen from German computer mag c't is researching the issue and has a lot of hard testing data available.