I just bought a retina macbook pro, and I got the model with the 750m graphics card. When I turned off the option that said automatic graphics switching in the energy saver section of system preferences, it gave me a message that said the computer would always use high performance graphics. However, I noticed some lag when I started using it, especially with animations. I went to the apple store, and told them the problem. They said that this was because since the NVIDIA graphics card has 2GB of memory, that acted as my RAM, and the 16GB was not actually doing anything/being used, and with the switch turned on, it actually uses BOTH GPU's (or at least they work together somehow). So he told me to turn the switch back on. I feel like since the computer told me that it would be "high performance", the guy at the store was contradicting what the computer was telling me...does this make sense? Was the guy at the apple store telling me to turn it back on because that's the default or something? Thanks.