I also bought an Ultra 90 off of the forums. I was looking for a cheap alternative to the Ultra 120 for overclocking my E6600. Here are my results from a few minutes ago, if you're interested. The Thermalright thermal paste has not settled yet but I doubt it will get much better.
My room is very warm - about 80 to 90 degrees Fahrenheit. I used an E6600 CPU on an MSI 975X motherboard and a Cooler Master Centurion 5 mid-tower case with the glass window (no side vent). Cables were tucked away, so they weren't a factor. I have the Ultra 90 positioned so that the long side is going up and down. I also may have put on a little too much thermal paste, but I used to cooler to smear it all around so that the excess paste is knocked off to the side of the contact point on the CPU. To get the load temperature, I put OCCT in the background, did some work on the computer, and checked back when the temperatures stopped rising.
The cooler uses the same pins as the stock cooler to stick itself to the motherboard, which means that the entire installation is toolless and does not require the removal of the motherboard. The pins are delicate, however, and will weaken/bend out of shape every time you remove and re-install the cooler. One of the pins on my cooler has broken but as long as you have two pins diagonal from one another intact, your cooler should be pretty firmly attached. Attaching the fan uses wire clips and the process is very easy and sturdy.
After testing every possible configuration with the positioning of the fan and cooler, I have found that the best results come from having the fan pulling air across the cooler and blowing out the rear of the case. If your power supply has a downward-facing fan, which mine does not, you may get better results with the cooler rotated so that the PSU fan blows into the cooler and the mounted fan is on the other side, pulling the air downward and through. Note that I am using a Vantec Tornado, so any other fan would probably yield results at least one or two degrees higher.
Without a Fan, E6600 @ 266MHz FSB (2.40GHz/1066MHz), 1.21v:
Idle: ~55 degrees
Load: Not Tested
The results are worse than the stock cooler. This is a given and consistent with the reviews I've read of the Ultra 90, so I wasn't surprised. I didn't dare test this thing at load, much less overclock. Even with a 120mm case fan a few inches away from the cooler pulling air out of the case, performance was unacceptable.
With a Vantec Tornado Fan, E6600 @ 266MHz FSB (2.40GHz/1066MHz), 1.21v:
Idle: 39-40 degrees
Load: 46-47 degrees
> For some reason the idle temperature is only a few degrees cooler than using the stock cooler. The load temperature is only 46 to 47 degrees, which is much better than the stock cooler.
With a Vantec Tornado Fan, E6600 @ 333MHz FSB (3.00GHz/1333MHz), 1.28v (completely stable):
Idle: 42 degrees
Load: 52 degrees
> At this overclock I get the same results as the stock cooler at stock speeds. Pretty good for exceeding the X6800 with second-tier equipment.
With a Vantec Tornado Fan, E6600 @ 360MHz FSB (3.25GHz/1444MHz), 1.38v (probably stable):
Idle: 46-47 degrees
Load: 59 degrees
> At these settings, the CPU goes up to 59 degrees under load but then stabilizes, fluctuating between 58 and 59 degrees. I am not comfortable with anything above 60 degrees for the C2D, although I am sure it can go a little higher with no problems.
Henny, can you check your settings? If you are getting temperatures in the 30's with 1.4v on the CPU, then I think I am doing something wrong as I have the most powerful 92mm fan available and I cannot get under 40 degrees idle at 1.28v.