I asked on a laptop games forum once and was told it wasn't worth it. The increase in frame rate would be only tiny and not worth the stress it put on the GPU, which would decrease its lifespan.
Getting the best driver for my graphics card was a much better way of improving performance, but required a little know-how. It required a 'modded inf file' or something, but was worth the hassle.
Might be different for desktops.