I OC'd an XFX 5770 to 960 core and 1350 mem (from stock 800/1200).
When I ran Furmark (stability test, Xtreme burning mode, windowed 800x600, 4X MSAA) it reported 23 FPS at 62 degrees.
I then kept the core at 960 and turned the mem clock back down to 1200 and reran the same test on Furmark.
This time it read 21 FPS at 50 degrees.
2FPS for 12 degrees of heat? I know 62 degrees is well within the safety limit for this card, but if all I gain is 2FPS I don't think I'll bother.
So, as the title says, any point to OC'ing the memory clock?
It doesn't help that much. You use the VRAM for rendering images and anti-aliasing etc.. so you might see more performance gain on a massive 30" screen or dual-monitors, but for the most part overclocking the already lightning fast video RAM is pretty wasteful.