I need to run my 6 core Intel 980X PC silently so I got the biggest heatsink I could find at a reasonable price... Yep, it's big, and it works well for me.
It comes well packed with a quite silent fan included and a couple of alternative chip/mobo attachments. Oh, it also comes with thermo paste so no need to buy any separately.
Installation was reasonably straightforward, and was about as fiddly as most other heatsinks I've installed. It's big and heavy so it takes some care. The most fiddly bit is fitting the fan because it clips on with springy wires, the instructions aren't great on this and it's a tricky job to get it to clip on. One piece of advice I'd give is to size the mobo up in your case but don't install it, decide which side you want or have to put the fan (the mobo might obstruct some sides for example), and then put the fan on with the mobo out of the case. Note, the fan fits onto the side of the sink, not the top.
As an aside, I'll just mention that this heatsink is too big to fit in my Antec P193 case. But that's not the fault of the Ninja at all because the P193 case has an internal side fan which reduces the space available above the mobo.
So, back to the heatsink... Installing the heatsink is one thing, but the included fan also comes with a PCI backplane plate to control the fan speed (which isn't really mentioned in the online specifications), so you have to locate this somewhere. I didn't have any PCI slots left in my PC so I just left it hanging around inside.
As a test I set the fan on lowest speed and stress tested my 6 cores at 100% for a 1/2 hour or so and had no problems at all with the temperature. Very satisfactory in this respect. The heatsink stayed warm to the touch throughout.
As for silent running which is what I need, the fan is not the best in the world and it has a slight clicking sound to it. But, running it at low speed makes it almost inaudible so I'm happy with that. My hard drives clicking makes more noise.
One more piece of advice - check that you really need a third party heatsink! It was unmentioned in any of the online specifications that my 6 core 980X intel chip actually came with a very chunky heatsink and fan completely free and gratis so I probably could have used this instead if I'd have known.