Try both, but I'd personally say exhaust. I had 1-2 lower cpu temps with intake on my 902, but my case temps got very hot inside with all the hot air coming off the radiotr going into my case. Of course now that I'm using a Silverstone Fortress 2, exhaust is my only option, in terms of mounting it up top.
"Basically - mounting the radiator as INTAKE will reduce CPU temperatures, the amount depends a lot on your case and your other hardware. If you have loud, stock coolers on your graphics card and less-than-fantastic exhaust fans then your system will get hot quickly. You'll be blowing hot air from the CPU all over the motherboard.
Now this isnt such a great problem at idle temperatures, and could be nice in some ways, since your CPU will stay dead cold and your fans will barely move. However, at load, your CPU may be running at 50C (assuming a high overclock, for AMD - even higher for Intel). Now I can tell you from experience that the Corsair is VERY good at moving that heat from your CPU to the radiator, and if you put your hand over the exhaust from it it's very hot. The thought of this blowing all over my motherboard, RAM, Graphics cards makes me cringe, it just seems so counterintuitive.
In terms of what you notice - intake will yield a couple of degrees better temperature, although really depends on the hardware in your system. If you have lots of graphics cards it's going to increase this difference.
The personal feelings of myself and most people in this forum are to ignore Corsairs advice, and configure the fan as EXHAUST. Note that we also see big improvements in temperatures when you use a push/pull setup.
Here is a blog directly from Corsair, and includes some of the testing they did on Push/Pull
Here's mine and the fans aren't that bright in real life lol
Edited by Jocelyn84 - 4/13/10 at 10:30am