I ran my i5 750 on the stock heatsink for awhile while I waited for Noctua to send me a Socket-1156 backplate for my NH-U9B (which they didn't, I eventually gave up and just bought one). The heatsink is indeed minimal, but the worse part about it for me was the fan. At anything above its minimum speed, it whines and grinds to a point that it really is annoying. Keeping all power saving features on and turning Turbo mode off, I ran my i5 750 at 1V Vcore with no issue. IIRC, it refused to boot .95V, but I didn't fine tune it from there. I also ran the chip at 3.4GHz (200x17) on the stock heatsink with 1.1625V, which was stable as well (although noisey).