To me, the INTJ is just a ISTJ thats evolved
If your thinking and sensing is at such a level then a critical mass occurs where you become more intuitive. Its like changing gears in an accelerating thought process.
Anyway, I believe I've met very few real INTJ's. Perhaps 2.1% of society type as them, but real INTJ's that I've come across are less than 1:1000.
What I have noticed is the following traits: (Not necessairly their good traits, just what I've seen).
1) Introversion is because they enjoy being in their own thought processes more than engaging with groups of people. I believe if you had group of INTJ's they would become more extrovert. (There's a big difference between being a "loner" and being a professed "introvert").
2) Always bouncing their theories off people they trust. Looking for feedback and binding information.
3) Loyal to those that have meaning to them. Because the group mentality doesn't mean anything to them they don't need to alter their position to changing situations ie Consistently reliable. (Being popular is just a function of having no baseline values -> well, in the extreme context).
4) More likely to get a left field observation of the world.
However, I don't think INTJ's are perfect though, the ones that have been in certain situations have had the edges knocked off them do get a bit more refined, others just become more introverted (than moderate) or fail to see (understand) why the "flesh pushers" get further up the tree.