"It makes the Ultra-120 look so awesome I wonder why they are so different."
Well, unlike those other three large heatsinks, Ultra-120 is designed only for fan-cooling, where as HR-01, Noctua and Ninja can be used both passively or actively. HR-01, Noctua and Ninja also work good with a fan and work very well with undervolted fans, where as Ultra-120 provides ultimate cooling at full fan voltage.
Pretty much everything in Ultra-120's design gives away it's focus on fan-cooling: tighter fin spacing, bent edges on fins (to reduce angle of attack of incoming air from an axial fan), etc. If it only had as many heatpipes as Ninja, it would be even more capable for fan-cooling very hot CPUs. (But it's still very capable in it's current configuration too.)
The results obtained using the heatsinks are pretty much what I would expect from the appearance alone.
"I have another look at the heatsinks, every time I read up about Ninja's it's the same thing about the fitting which scares me a bit, I can just see myself not hearing the click and pushing until the board is in two pieces"
If you take the motherboard out of the case, there's little chance of that happening. Scythe continues to insist it's "not necessary" but they have to defend their marketing claims of "easy" installation compared to every other heavy-weight heatsink. In fact the weight as well as center of gravity of these monsters may be one reason why push-pins don't work on Ninja as well as stock Intel cooler (not that Intel coolers are anything worth comparing to).
Bad thing is, even if you mounted the heatsink properly (taking the motherboard off), it's still not something I would guarantee to provide adequate contact for the whole life-span of the system. Only removing the pushpins from the bracket and replacing them with screws (and adding a backplate behing motherboard where to screw those screws in) can eliminate this mounting issue for good and ensure it won't come off later.
"I'll definitely check out the Noctua the mounting process looks a lot easier, cheers!"
It's easy if you pay attention to what your doing. There's lots of mounting equipment and some may look similarish but are meant for different sockets. If you have both the IQ and patience of average person, you would probably find Noctua easier to mount than mounting Ninja (properly).
Where as Ninja has good mounting method for each socket except 775, Noctua is the other way around, being most versatile on socket 775. On some other sockets, some older versions of Noctua may only be operated horizontally which may provide less outstanding performance. Recent Noctuas should come with adapter brackets to tilt mounting 90 degrees on K8 and AM2 brackets.
Mounting it vertically (thus exhausting hot air toward exhaust fan of the case) would provide some extra cooling efficiency but (not only might it be limited to socket 775) it might also be less rigid as horizontal mounting. I'm not sure about it though. It's just that with vertical mounting, the two screws with load-limiting springs are attached to both sides of the heatsink, possibly allowing the heatsink to rock up and down and tilt down due to gravity. That problem may exist even with horizontal mounting as those screws do have a spring load to prevent over-pressure to CPU die. [what I mentioned in this paragraph is unlikely to occur based on some pictures I found later]
I have to emphasize that I have not (yet) read about or witnessed such tilting down due to gravity... not with Noctua. HR-01 review did have a picture with quite severe-looking downward tilting. Reviewer recommended supporting the heatsink up to prevent it tilting down. While I'm not sure if Noctua, Ninja or Ultra-120 needs such a thing, it wouldn't harm to at least check if the heatsink is tilting after assembly and then give extra support if needed.
Noctua might have a better sideways support... might or might not. It would probably depend on whether spring load will press the mounting bracket tightly into contact with the mounting legs (that are screwed through motherboard to backplate) or whether springload pushes CPU down and CPU will provide adequate force to keep these mounting bracket from physically touching the mounting legs. I tried to find pictures of assembled systems using Noctua but did not find any close-ups or high-resolution pictures take from the right direction to allow perfect view to mounting pieces.
Here's some feast for the eyes:
http://www.dvhardware.net/review110_noctua_nh_u12f.html
That's a review that really shows the beauty of that cooler. Especially the pictures of second page.
And I finally found a picture which proves that (at least if no spacer is used between CPU and heatsink) the mounting bracket will be in physical contact with the hard mounted leg pieces. Also, mounting bracket is wide, thus should prevent rocking in that direction as well. Well... here's the picture:
http://www.matbe.com/images/biblio/art_ ... 025100.jpg
Here's a picture of tilted Thermalright HR-01. http://www.silentpcreview.com/article290-page4.html
It appears to be more tilted than it really is, because motherboard is a bit tilted too. But take a sheet of paper, put one of the edges paraller to LPT1 port and line up a perpendicular edge to heatpipe of the heatsink. They don't line up! The heatsink is noticeably tilted even with bare eyes. Just noticed HR-01 isn't even available for Intel sockets...
While Noctua isn't as good a performer as Thermalright Ultra-120 or Scythe Ninja under high-airflow conditions, and while it's still among the best in low-airflow cooling. If there's no recent revision of HR-01 that will mount to socket 775, it might be
The cooling solution for low-airflow cooling for 775. Question is whether low-airflow cooling is enough for your E6750. It may (or may not) be slightly inadequate for my Q6600 and I might end up not running it passively and thus Ultra-120 might have been "more ideal" for my Quad. It would have cost more and it would not have come with a very quiet Noctua fan bundled with the heatsink, though. Also, cooling CPU is beneficial only to a point, and anything more is just excessive. Since I have no plans of overclocking, there's little real benefit from Ultra-120 to justify extra 30 eur (10 eur extra for HS itself and 20 eur for a high-quality fan).
It's "funny" that Noctua HS comes with a fan even though it's capable of running many low-end CPU passively (providing adequate case airflow), but Ultra-120 which is completely useless without a fan, doesn't come with a fan. Well, at least it's better to have a lower price and let the user choose a quiet fan (like Nexus) instead of bundling a noisy fan that will end up replaced and trashed. It's also a good thing that Noctua HS comes with Noctua fan instead of any other brand. Noctua fans can handle very little backpressure but are also very quiet. Since Noctua heatsinks have widely spaced fins, the fan should be perfectly suited for it. And Ultra Low Noise Adapter (ULNA) is a good adapter too as heatsink is designed to operate on low airflow. Ultra-120 might work better with a Nexus fan instead of Noctua's due to Ultra-120's tightly spaced heatsink.
I think you might compare the good and bad aspects of Ultra-120 to Noctua instead of Ninja (which roughly is somewhere in the middle when it comes to whether they are low or high airflow type). Ninja may just require too much modification to mount it properly. (It's also a way of telling Scythe that we want the old mounting method back. It's pretty much the only way to tell them that in a capitalistic world. Sending angry e-mails doesn't help much as they will always claim that majority is happy and that it's always the unhappy minority that gives any feedback.)
Well, that was a long post... again. It always ends up that way when I'm writing.