I have just finished my second shoot using the NN5. I want to discuss a limitation of the NN5. I think it is better to consider this a limitation rather than a criticism. I assume that this would apply equally to the NN3. The limitation I am speaking of is that the NN may not be a good choice for long exposures. It does not help minimize vibration and may in fact amplify it.
The shoot was made from the summit of a small mountain on an island in San Francisco bay. Wind was light but steady. I shot from late afternoon around 6:30 until early night 9:30. I wanted to get daylight, sunset and blue-hour panoramas. The daylight and Sunset shots were fine. The daylight and sunset exposures were all 125th or shorter.
However the blue-hour shots were 3 second exposures and the results were disappointing. The shots not only showed some general é─˙non-directionalé─¨ fuzziness which I attributed to the wind and atmospheric distortion of the light but also some definite linear vibration. I believe that the linear vibration is attributable to the vibration of the shutter traveling as a wave back and forth through the two arms of the NN. Looking at the NN design it seems obvious that vibration might be amplified by its structure. This same distortion appeared consistently in all of the 30+ exposures I made using a 3 second exposure. Of course I used all of the normal tricks to reduce vibration such as mirror lock up and 10 second shutter delay. Since no similar distortion appeared in the shorter exposures I believe that the exposures were shorter than the wave frequency of the NN.
In retrospect I wish I had used my conventional ball head. Almost all of the important features in the image were 2-7 miles away and so parallax would not be an issue.

I would like to say otherwise that the NN seems to do a good job with shorter exposures. I had no difficulty in setting it up and determining the right settings for my camera and lens.

I would recommend it to other photographers with the caveat that it may not be the best choice for long exposures.