First, there's no way for them to tell that you've OCed unless you scorch the thing. Since I'm on water-Asetek push/pull dual-fan system-unless the pump goes out while I was stressing the heck out of the CPU, I'm not that worried about my relatively mild OC.
As for other tests, the only one I value is the FPS boost I saw when I first tried Skyrim with the new OCing. Well over 10+ FPS, though that's a bit of overkill for my card. I haven't tried going back to the vanilla clock for The Witcher 2, another CPU-intensive game, but I do think that the OC is why I can use the Uber-Antialiasing setting without going SLI.