I went to see how far I could OC mine without a voltage bump, and compare stock to the straight multiplier OC, and i got to 4.2 completely stable after like 19hrs straight in Prime 95. I also saw immediate performance increase, and also reset the OC and then brought it back up again just to make sure I wasnt just making sh** up lol.
Yes, OC it, you will see performance increase in ANY CPU intensive game, and a small increase in performance overall throughout any program, and even within just Win7 Desktop lol.
OCing your GPU as well, especially since you have a 570, will also net some solid performance increase. Though, I cant help with that one since I am holding onto my 275 till the end lol
With the 2500k though, I say OC the crap outta it, thats what it was designed for. Also take into accnt that when Intel releases a CPU they WAY underclock it factory to make it accessible to people in any climate, with any bottlenecks, etc etc. These chips were designed to go WAY above and beyond what they are set to, right out of the box, so do not be afraid of some volatage bumps and multipliers. Watch your memory too as you start to OC, might have to make some adjustments there the higher you go. Deterioration only starts after a couple years of a very intensive voltage bump/OC that has been running 24/7 like in a folder or miner. Other than that, you can rely on a solid OC for a while. Now go get too it! This is OCN for gods sake!
(its hard to ruin a CPU with a mild OC/voltage bump, even running 100% for 24/7, so dont worry, you will be fine lol)