Yeah, I overclock my i5 2500k to 4.3Ghz (I pushed it to 4.9 on air cooling for fun), but it's not an "always on" overclock. Most times, the CPU drops to 1.6Ghz when idle or for light-duty things: web surfing etc. The "K" series is designed with overhead in them and there is a safe range. I have a massive heat sink and many fans, and even when gaming my CPU barely gets warmer then the warmest Summer day. With today's CPU's most folks don't need to overclock. Your video card(s) are more important to game-play, though I did see my games play a bit smoother with a bit of a frame-rate bump when I OC'd.
I also like to hack my toys to get more out of them: CPU, video cards, router, DVD drive, AppleTV, PS3, PSP, tablets etc.