It's pretty pathetic for NVIDIA to write drivers that require the use of 3rd party utils to achieve sane fan behaviour. The GTX260 I bought was the first video card that I'd bought that required such a massive cooling solution, and I thought that since the cooling hardware seemed fairly capable, the software wouldn't be a problem.
Imagine my surprise that, by default, the fan is set to run at 40% without *ANY* ramping, and only jumps to 100% when the card reaches ~85C - when it's basically overheating. Thanks NVIDIA but I'd rather live with a bit of noise from higher fan speeds than turn my case into an oven.
You can download an addition to the NVIDIA drivers that allows you to manually set the fan duty cycle (which works), load profiles with alternate fan duty cycle % depending on temp (which works, badly, because the profile loading locks the comp for a second, and this isn't fun when you're playing a game), and set a fan ramping profile with a graphical curve (which has never worked, and since it's been 2 years, I can only assume never will)
Why they can't fix this is beyond me - RivaTuner is capable of directly reprogramming the fan controller, and is trivial to set up to smoothly ramp (without any CPU load) the fan speed in response to GPU temp. 40% at 40C and 100% at 65C. On demanding games I usually top out at ~61C and 80% fan speed. Sure it's a bit noisy, but that's always been the price of good cooling (barring some exotic expensive solutions).