Pretty mixed feelings about them. The Ni dominant thing is a mystery to me, and as much as I can appreciate it for its brilliance at some occasions, it really goes on my nerves how the consider it an objective source of truth, to which no objections apply, because they 'just know it' and 'it is so'. I am a person who needs to know the why-s and can't put such blind trust in those freaky insights, and am way more straight forward in my reasoning, although outwardly appears the opposite because of their Te.
Talking about the Te, many people seem to find it the most annoying thing about INTJ-s, but I'd frankly say that for me it is this weak egocentric Fi. They don't even realize how their whole approach in debates is based on emotion and vulnerability, which totally keeps them away from the thought that there may be some truth and reason in the other standpoint, and some logical flaws in theirs due to too much generalization and overlooking some nuances. I can't explain to them that the fact that they are good orators and sound right doesn't make them more right than they are. But all the Te-Fi thing seems quite utilitarian at its core.
Anyway, I kinda like them. Maybe because I'm on the borderline with them (P/J is like 51/49). Still, I'd rather debate with an ENTP.