I saw around 9C drop in temps with my 7950s replacing the stock TIM with IC Diamond, and that was with less fan speed.
My reference on air 470s saw an even greater improvement replacing the stock TIM, I pretty much swear by it now.. And it's even more important now that both companies are using temps to throttle.
From the IC Diamond, which I personally wouldn't recommend for these bare die's we're seeing now (due to scratching)... To the CLU I saw another 3-4C drop at the same fan speed.
I never cared for my TF3's fan noise over 55%, so it was vital for me personally to get them to transfer heat as well as I could because I normally ran them around 60C with 47% fan @ 1100 core.
That's a pretty big difference. Any recommendation on how to apply it without getting it on anything else but the die? I assume just a thin coat on the GPU die only?