Google Chrome immediately triggers the dedicated card on my machine, Safari rarely triggers it so trying to use Safari more. I've tried ML and the newer Safari on my MacBook Air but I'm waiting for the release to install it on the RMBP. Safari in ML is finally good enough for me to switch off of chrome. Unified address/search bar plus tab and bookmark syncing is all I need. But back to the graphics, there doesn't seem to be any good reason for some things to use the dedicated. However, the retina display may need the card a lot more than one would think. If I had a non-retina, I would turn off the discreet as I know my 2012 Air does fine with its integrated 4000.