Hi, I have the same video card, although mine is from Asus and memory is clocked to 900mhz and not 1000mhz like it is advertised by Nvidia... I overclocked it to the maximum just to test and increased memory frequency to 1100mhz, noticed an increase of 8 fps or more while gaming and temperature only rose up about 3º/5ºC.
Don't listen to negative comments of people who don't understand this, if you manage to control your temperatures and if they don't get much higher than the non overclocked version then you are okay. For example if your temperatures are not higher than 85ºC then you're fine, but if the temperature go higher and if it reaches 88º/89ºC it will thermal throttle so the performance will decrease making OC not effective...