HD4000 graphics is actually very capable. It can run 90% of the games out there with no problem. People think games like Crysis 3 are the rule for games. When they are actually the exception to the rule because most games don't require that much HP to run.
New games like Transformers: Fall of Cybertron have great graphics and can run on MAX settings with HD4000 graphics. I've had HD4000 graphics on a laptop of mine with a i7 to go along with it. And I had no problem running games like Borderlands 2 and CODII Black Ops on lowest settings. Even MMO's like World of Tanks ran quite fine with low-medium settings and this games fairy graphics intensive.
So by overclocking HD4000 graphics it'll only get even better performance. I was gaming on a 1600x900 screen, but I imagine that a 1920x1080 screen won't be much different and could still play the games I've mentioned. Although games like Crysis 3, Far Cry 3, Metro 2033, and Battlefield 3 probably won't be playable even at low settings. I'm sure you could still play them at 1200x800 resolution at lowest settings with 25-30FPS. So either way, you can enjoy almost every game. And for integrated graphics that's pretty good.