MacBooks have great battery life for a few reasons, including, but not limited to, GPU switching. However, as Ubergizmo discovered, when you run Windows 7 in Bootcamp the GPU stays on all the time, essentially sucking down battery like a fiend. The 2009 MBP also had issues – the screen was too bright and the keyboard backlight was always on – but otherwise there wasn’t much of a problem.
However, with the GPU always on you move most rendering from the power-sipping processor to the power-sucking NVIDIA GeForce 330M. Sad, but true. But what are you running Windows 7 for anyway? Quicken?