For many intents and purposes, the LG Optimus G is fundamentally the same smartphone as the hotly desired Google Nexus 4, aside from some differences in form factor and the fact that the Optimus G doesn’t run “vanilla” Android. However, it looks like the LG Optimus G could soon be a “better” Nexus 4 with the port of CyanogenMOD 10.1. The custom ROM is based on the Android 4.2 Jelly Bean build that is found on the Nexus 4. It strips away that LG Optimus UI and gives you the free CM experience that you’ve come to expect from previous CyanogenMOD builds. This is an early build, though, so there are problems. The WiFi, NFC and capacitive keys don’t work yet, for example, but they’re hopeful it’ll all be fully functional by year’s end.
Remember that the Optimus G ships with just ICS under the hood, so this is likely a much faster way to get to Android 4.2 than waiting for an official update skinned by LG. Getting to load these custom ROMs is easier too, as there is a $1 app in the Google Play Store called FreeGee that allows you to unlock your bootloader and remove LG security. You could still bootload the old school way, but the app is easier.
Should you want to brave the early build on your LG Optimus G, you can find the CM 10.1 download on XDA. As with all these kinds of mods, proceed at your own risk and discretion.