As some of the other users have suggested, try grabbing gfxCardStatus 2.1. I was initially worried at the battery life I was getting and started to dig into things.
Launching Chrome, Firefox, Keynote, or Skype triggered a change to the discrete graphics card. I have an early 2011 MacBook Pro 15" 2.2GHz i7.
Right now I am working in InDesign CS4 (which oddly does not trigger the change, Illustrator and Photoshop however do.), Word 2011, Safari, and running iTunes in a fullscreen mode off to the side. With 40% of the battery remaining, I have @ 3 hours of charge left, however it does fluctuate down to 2:30 depending on how much I switch between Word and InDesign.
I colleuge was having the same issue and was able to replicate the graphic switching issues on his 2011 MacBook as well ( 2.0GHz i7 15"). I am not sure if this is an OS issue or application one, but hopefully this narrows it down for some people.
I am getting slightly better battery life with the integrated graphics, average when the discrete is turned on and using an application, slightly less when the discrete graphics is under a heavy load (World of Warcraft or Starcraft II)