Check this out:
I switched to the integrated graphics in my 17" MacBook Pro. Not only is battery life way ahead of what I was getting with the dedicated graphics, the machine runs a lot cooler and I don’t see any difference in performance. As long as I’m not playing 3D games (which I never do) or doing heavy lifting in Aperture, there is no reason to use the dedicated graphics. The only real downside is that a good chunk of RAM (maybe 200MB?) is sucked up to be used by the integrated graphics chip. Not a huge deal, though, unless, once again, I’m doing a ton of work in Aperture. I’ll have 8GB in this thing one day, though. Not a problem.