I'd like to manage fan speed too. It Seems that the system doing it a little, sometimes fan is turning faster (and makes more noise), even if it's long the fan goes back to its original speed as soon as the CPU is less used. it seems that fan is running at a 30% speed and goes to 50% when CPU is working hard (only a comparison with fan noise heard with eeectl on windows).
About SpeedStep I've not been able to handle it correctly, now I'm using application named CoolBook.
This apps let user to choose speed and voltage, it displays too CPU temperatures. It's shareware (around 10$) but it's a good investment.
Sadly this apps doesn't provide a way to mod fan speed.
I keep searching around, if only i could lower the fan speed to 20%-25% :)