I'm a little surprised by the answers so far even if they speak to some form of truth.
- Do you upgrade every couple years? If Yes then OC / If No, you'll need to OC to continue getting respectable frames
- Do you like the idea of a GTX 980 performing around the stock GTX 980ti? If yes... then OC
- Do you have a 700 or higher watt PSU and only 1 GPU? If yes... then OC
Overclocking is just free performance, Nvidia cards and the Maxwell series are known to be highly overclockable.