The LG Optimus G is a pretty old device, and it had been on the Android 4.1 since a long long time. And considering the fact that the KitKat is optimized for old devices as well, the company has decided to update the smartphone to the Kitkat version. Though LG did not tell much about the update, and whether what all new features and improvements will the update feature.
But we suspect that the update ouwld naturally boost the performance of the device, and also bring in some KitKat default features like the Google Now and hangouts integration. As what we had seen in the LG G2 after the KitKat treatment. So similar changes would be brought in the Optimus G also. So LG Optimus G users just hang on for the update, may be it is the time to revert back to stock ROM and unroot your devices, if you were experiencing the KitKat through custom ROMs.