Is graphics card overclocking worth it? In short, yes it can be. Certain configurations respond well to the change and after all, it's free and mostly safe. However game changing results should not be expected.
In our tests we saw modest gains all along, and the mid-range GeForce GTX 560 Ti seemed to be the card benefiting the most from bumping the stock specs. In the best of scenarios your games will play a bit more smoothly if you are not pushing the GPU beyond its real capabilities. In the worst of cases, you won't gain anything and you can dial things down back to normal.
In the four games that we tested the Radeon HD 6750 delivered on average 3fps more when overclocked, a 14% performance gain. The GeForce GTX 560 Ti averaged an extra 6fps for a 13% increase, and the Radeon HD 6970 averaged 3fps more for a 6% performance boost.
AMD and Nvidia are being extra very careful about how they build their GPU series now. They almost never offer a card that can be overclocked to replace the model above it, you can only close the gap. You might be able to overclock the GPU higher but other factors like memory bus width will always hold the performance back. This goes in stark contrast with the latest CPUs which appear to be wide open to enthusiasts' abuse and potentially huge performance gains.
Going to these extremes for the sake of overclocking is probably not worth your while with the current crop of GPUs -- at least not if all you care about are raw performance gains. Image credit: xtremesystems.org
But back to the GPU world, where overclocking may not make sense is when it is carried out by the manufacturer. Factory overclocked cards almost always cost more than the performance gain provided. For example, last year we reviewed the HIS Radeon HD 6850 IceQ X Turbo which was priced 15% above that of a standard Radeon HD 6850 graphics card, yet only provided a 4% performance improvement.
While it's true that more expensive factory overclocked cards usually come with upgraded coolers, an added bonus that goes beyond raw performance, there are many similar upgraded cards without the overclocking that retail for less.
What's been your own experience? Do you overclock your graphics card these days? Did you use to? (please keep the Crysis jokes to a minimum :)).