Another positive is that we can talk about damn near everything for a damn long time. It's intellectually stimulating.
I believe that this compatibility relies heavily on the individuals personal confidence level and consciousness <higher functioning>. This relationship has a way of making both partners feel exposed in ways that they haven't been with other people. It happens so quickly the INTJ is left in a head spin and the ENFP feels extremely vulnerable without an element of having built a foundation of trust. It's perplexing.
I'm attracted to my INTJ because I can sense him. He doesn't even have to finish sentences, I know what he's thinking and can follow that thought process, elaborate on it, and comment appropriately. He finds that to be a fascinating trait because it's rare. He also is attracted to my balance of intelligence and emotive warmth. Plus, there is an added draw of the nerd getting the hot chick element at play.
Complimentary aspects are pretty much everything. I'm everything that he is not, and he's literally verbalized that. Vice Versa.
Understanding comes with some time, but I'd have to say that I started to understand that while he may not emote feelings he still has them. Once I accepted the general blanket principle that he likes me so much that he's spending all his free time with me and doing things he wouldn't normally do it was clear without using words. I actually knew how much he liked me when he showed up to a large social event planned for my birthday at a very obnoxious and noisy club environment. Then, when he wanted to leave, he wanted me to come with him. I declined because I wasn't ready to go and he lingered and caressed my arm. At that point, I let so much of my guard down that I almost fell in love with him right then. He understands me better when I'm minimally emotive. As long as I bring him clear, concise communication about what I want he's exceptionally accommodating.
We do not have children together but he lights up and truly emotes around children. He feels most comfortable with them as they are not apprehensive and expecting.
When it's not working:
Sometimes his lack of emoting causes me insecurity. This makes me feel uncomfortable and I tend to clam up. Shutting down communication doesn't help us work through issues as quickly so progress in this areas is sometimes slow. Although, we compensate for this with an incredible amount of patience for one another.
Another thing is that he fatigues easily in social situations. He likes one on one time with me the best. I try to remain mindful of that instead of expecting him to attend large social functions for long periods of time.
Biggest frustration from my end is how vulnerable I feel with him. I'm completely raw and bare; emotionally naked. There is no hiding from and INTJ. I intuit this and know it's best just to answer the hard hitting grime of questions which for me becomes exhaustive.
Taking each other for granted - I could probably rely on him to take care of everything task oriented (i.e. putting a budget together, keeping a time table, industrial nature chores, etc)
As for him - He consistently misinterprets my signals and flirtations which I use to express my desire to connect with him. It's somewhat lost on him. So I cannot be a flirty romantic. I have to spell it out for him directly, clearly stating what I want, and let him take the reigns. And he does. For instance, if I feel like I want to spend time with him - I cannot say "I miss you" because he'll just say something like "OK", or "Thank you". Instead I have to say "I want to spend time with you". He knows what to do with that.
My best recommendation is probably not far off from what I would tell any couple attempting a relationship. But for this one specifically I'll say this
INTJ speak rational and semantics. ENFP speak emotion and concepts. Learn to speak the language of your partner and communicate in a way they understand. ENFP's need to be clear and concise with the expression of what you want. Think of it this way - give him something he can act upon rather than a social construct to respond to. Then respect his idea and tell him thank you. That's what has worked the best for us.
INTJ's need to provide assurance without labeling neediness or clinginess. Another good point for INTJ is to alter the paradigm of expectations. You can contribute efficiency to and ENFP's life, but would be wisest not to expect ENFP to initiate thoughts/ideas/behavior patterns to become more efficient. It's not in our nature. Very much the same way emoting isn't in INTJ's. An ENFP expecting INTJ to emote would be likened to that of an INTJ expecting efficiency from the ENFP. Vice Versa
It would also suffice to say that ENFP shouldn't take what INTJ says personally or to heart. With my INTJ, I've literally asked him to tell me when he needs space. I don't take that personally. I think I will ask him to add to that statement that he'll come back after the isolation.
That's all I've got! Hope this is enlightening.