I have quite a bit of experience with the INTJ type. They are largely positive, as being an INFJ the INTJ has a lot in common with Ni being the leading function. There are some difficulties between the two types due to the opposing creative functions Fe and Te, which correpond to each others point of least resistance, the function that is most likely to cause irritability should pressure be applied. In social circumstances this doesn't seem to be much of an issue. Also, socially I think that perhaps this gives INFJ type the upper hand as we can interpret the emotional situation and tailor our responses easily, while the Te of the INTJ can do some logical heavy lifting for me.
To clarify, since this is mainly an MBTI forum, the super-ego functions according to Model A in Socionics describes Te and Fe as the most sensitive and likely to irritate the INFJ and INTJ repectively. The other way around, these are the secondary, functions of the respective types which means it is how we mainly interact with the world on a concsious level. Given this, I think it is what makes communication between myself and INTJ types very engaging as we feed each other and perhaps make up for our own insecurities.
Now for some my own specific experiences... My father is INTJ, my childhood friend is INTJ, and one local I have befriended recently is INTJ as well. I also had a friend whom I've lost touch with a while ago, who typed himself as INTJ (the other INTJs in my life I have typed by myself as they were not aware of MBTI/socionics). This friend was older than me and we had a very close "kindred," spirit sort of friendship through which we were able to confirm many things about ourselves and progress in self-knowledge in a very pleasant and easy way.
What I've noticed is that the INTJ and myself make excellent conversational partners as we can relate to so many topics readily and seemingly never run out of material to discuss. I believe this is largely due to a similar way of processing Ni through the ego, as well as the almost-unconcsious or blatantly obvious unspoken use of Ne, which comes through from the id in conversation and action.
Some problems and benefits between the two types were noticed through interactions with my father, God bless him. He is a man who knows me well and who sees more readily than most the flaws in my behaviour.
This seems to be because Te is a difficult way of dealing with the outside world and always was a weakness for me. At the same time, it is not such an insurmountable barrier as with the ESTJ or ENTJ who have their leading function directly applying scrutiny on my Te or otherwise my most vulnerable function. Seriously, screw those guys.
Where my father can react amazingly in high pressure situations by distancing himself emotionally and acting precisely (an example, he has avoided a dangerous car crash with absolute grace and a detached and automatic sort of way, whereas I am a fairly good driver but cannot react in the same natural way in a critical situation). This is his use of Te in action along with the Ne and Se we share in identical positions along our cognitive stacks.
On the other hand my father, as well as my INTJ friends through my eyes, always had much difficulty in getting the desired emotional response from others in the social situation. I see this weakness readily as this is my creative (second) function and I am adept at navigating the world through it, with the help of my Ne function.
I now work as an electrician by the way, but my father - also a licensed electrician (and technician in various fields including IT) for many decades - used to run a business. When father and I have worked together on a construction project when I was younger, or doing renovations, he had to take extra care to explain to me his line of reasoning, and I could then respond very easily with my social skills. This way we could play off one another's strengths to get the job done right efficiently. If there was no communication from father, there would sometimes be conflict and difficulty organizing ourselves. If we got the organization done well, we could really enjoy ourselves and indulge in the Se function among the other aspects of our extroverted selves in our workflow.
This workflow partnership rings true today when I work on anything requiring action and teamwork. Additionally for me, being able to immerse myself in the moment is pleasurable whether I am working physically or doing creative arts projects, such as performing with music. INTJ shares this satisfaction with Se in the same position of the cognitive stack.
Another case. My childhood friend whom I have kept in touch with - despite living on the other side of the country for a few years now - can get together after a year of separation and converse as if the friendship was never interrupted. So can I readily enjoy time with my local friend whom I while sharing imaginary worlds and intuitive views that feel natural to us both.
......Where others have issues with Ni-leading types, I like to think I can understand why. Not many see the world the way intuitives do, let alone those with Ni as a primary (or secondary/creative) ego function. It is exactly this similarity in our internal worlds with Ni types that makes it easy to cherish these friendships all the more, to appreciate our imaginiative natures, and to understand the differences in how we metabolize reality, helping me personally to overcome our differences, which mainly stem from our respective weaknesses and insecurities.
To ignore this key difference (Fe vs. Te as creative or insecure/irritating functions respectively) would cause un-needed tension, so in social situations I am learning to be mindful and not offer unhelpful advice on social skill. As well, to remind a coworker or partner in a technical situation to communicate well rather than just get straight to work, so that we can work efficiently.
In other words, I appreciate all of my INTJs and think we can keep our relationships strong with relatively low energy expenditure, and some relationships, for life.