Good to know, thanks. I'd only ever run it in manual mode anyway. How is the computer supposed to know whether power or speed is more important at any given time?
It doesn't really, anything using OpenGL / CoreGraphics triggers discrete graphics.
Even silly things like the mail client Sparrow. I had to use gfxCardStatus to get anything more than 2-3hrs of battery life because my mail client is trying to get "fancy" on me.