This discussion has been fascinating. I've used and appreciated my Ni-dom all my life, but was as hard-put as anyone to explain it, since I have always just taken it for granted. PeaceBaby asks: does Ni give you comfort? I was about to answer yes, of course, remembering all the times it has shown me the way, like a light at the end of the tunnel. Uumlau, however, reminded me that I was jumping the gun, focusing on the results. There is unsettledness, even angst, in the time between the initial flash of insight, and the rigorous vetting and fleshing out of the idea using other functions. Waiting for implementation or results is also a stressful time. The tendency for contingency planning assuages this significantly, though one must then wait to see which contingency will need to be played out.
We may be attempting to do the almost impossible here, however: to define a function in a vacuum. That's not how we use them. Even our dominant function always works in conjunction with other functions. The interrelation will vary with the strength of the other functions and their appropriateness to the situation (degree to which we are calling upon them). Perhaps the trust I have learned to have for my Ni comes from its demonstrated track record when properly supported by other functions, particularly Te, Fi, and Se (logic, values, observations).
Here are a few examples of my own use of Ni:
1. Several things were going wrong at work. Colleagues in a different facility were being uncooperative about a collaborative effort. Beancounters and other "ancillary folk" in my building were making it increasingly difficult to get work done on a related project. On top of it all, a major reorganization was looming. Everything was a huge muddle. I was sitting in a dull meeting unrelated to any of this, when I heard a stray, tangential remark from someone I barely knew. It was like the magic missing piece of the puzzle. I instantly saw how all three problems could be productively addressed through one unorthodox but forward-thinking venture. Within minutes, the broad outline of a comprehensive plan formed almost on their own in my mind. Several weeks later, extensive research supported this basic framework, and sold it to immediate and middle managers who were impressed with what I had come up with so quickly. The proposal finally stalled when the senior manager was replaced by someone with no foresight and no courage.
2. Someone was hired at my workplace almost 5 years ago, on the condition that he would eventually relocate to one of our other facilities. I knew then that he never would, and he didn't (quit last month).
3. I was briefly introduced to a student several years ago, during a large meeting at her university (her involvement was tangential). I knew we would cross paths again. Two years later, she contacted me about a job. Her skills were a poor fit with my group, but I knew she would find a place somewhere, and already had contacts to whom to refer her. She was hired a few months later.
4. I recently had the master bath/dressing area in my house reworked, including moving walls to be more space efficient and to allow expansion of the next room which was uselessly narrow. I sketched out the new floorplan, but couldn't fit in a door between the bathroom and the closet/dressing area; there was no room left on any wall, but I didn't want it left open. When I realized I didn't need to have the walls intersect at right angles, I saw instantly that a very convenient door could be placed at 30 degrees to the neighboring wall. (I made other modifications to my house based on similar use of non-standard angles.)
5. Toward the end of a long dry spell in my spiritual life, I stumbled upon a notice online for a prayer group meeting that piqued my curiosity. It was a group I had never heard of, about an hour away in an area I had never been to, no one I knew would be there, I had another commitment that evening, etc. etc. Somehow, though, I knew I would attend. If this was prophetic, it certainly had a self-fulfilling aspect to it. I went because I made it happen, but everything fell into place effortlessly for me to do so. It turned out to be a major turning point in my spiritual life. (Now that part I did not forsee.)
6. Very simple: the phone rings, and most of the time, I have a good idea who is calling, and I don't have caller ID. I just somehow instantly cross-correlate who ever calls me, who has called too soon to be calling again already, what time of day it is, what might be going on to prompt a call from a specific person, etc. etc. A couple years ago, my SO's father was fighting cancer. He was doing reasonably well in treatments, but when the phone rang one evening, I knew right away it was to tell us that he had died.