My God is this awesome. The good news is, I'm not a bias reviewer, I'll also include the two bits that I'm not so happy about.
This thing is huge - there's no other way of saying it, and when it comes to air cooling, the larger the surface area of the heatsink, the better the cooling performance, in theory. The good news is that this goes with the theory.
You must remove the motherboard from the computer to get access to the base of the board. The small heatsink in the picture cools the CPU from the bottom, and surfaces just above the memory. Installing the bracket for the main heatsink is easy to do, the manual does make it clear and although there aren't many pieces for each CPU socket type, there are a lot of pieces that you probably won't use. The main annoyance is screwing the heatsink in with the two spring loaded screws. A plate fits over the base of the HS and is screwed in at either side. There is huge potential for the HS to slip about all over the place, mine did. You need a long screw driver and patience. I will mention that although mine slipped about, after removing the HS to re-fit it, i noticed that the thermal paste hadn't moved and was still in the correct place, so all good. Install time, 1 hour - carefully.
Two fans can be fitted to the main tower in a push/pull configuration and one can be fitted on the smaller heatsink. They all attach using 2 fan clips, and no screws - so very easy to install, providing the board is still outside of the case. Fans can be installed when the motherboard is inside the case, but it's difficult. The large HS can take two 140mm fans, and the little one can take an 80mm fan.
As I said, this is awesome. With no fans my CPU temp was about 5 degrees lower than my cooler that came with my intel Q6600 (originally 30 degrees). But with one fan it runs at about 18 degrees C, which is almost room temperature. Superb.
The harder your PC works, the better the heatsink will work. At 100% cpu use for an hour on a quad core, temperatures were at 25 degrees and the whole heatsink was warm, but not hot.
This thing looks amazing, I'm not compensating for anything :), but anybody that sees it will think "cool". The small heatsink doesn't get very hot, but it's an added feature and it can't hurt.
Note: If your power supply is next to your CPU, the small heatsink might not fit (meaning the whole thing wont). Before you buy, check out the dimensions and see if it will fit, mine does.... just. If it doesn't fit - make it!