I can share my experience with you, not sure how typical it is though.
I'm a female INTJ who had/has a casual relationship with an INTP (I met him when I studied abroad in England, so we knew our time together would run out eventually, but I say *has* because he's coming to the U.S. to visit for a vacation). I normally struggle greatly with relationships and finding people who meet my long list of criteria, but this is the easiest time I've ever had accepting and enjoying someone. He is 7 years older, so at the maturity level I want - may be a big contributing factor. Anyway, here's how it went:
We met on my first night in England, on New Years. My friend and I went to a party at a music club in London (I chose it specifically to meet people with my interests), and we were dancing together for a while next to this other group of people. I myself would probably never outright hit on someone or engage in conversation, but I could tell this guy next to me was looking over at me, and after a while he asked if he could by me a drink - a little surprising after getting to know him, but he is more extroverted than the typical INTP and very confident.
We saw each other several times over the couple months I was in England and got along very well. I was really comfortable around him, didn't feel pressured to make small talk; we found out that the major I'm studying (music business) was what he had gotten his degree in, and had stimulating existential/intellectual conversations over wine, which I could tell made him very happy (and me as well). He was resilient enough to put up with my argumentativeness and criticism, and wasn't afraid to stand up to me and insult me back (which is a must for me), and we didn't feel the need to text/keep up with each other between visits. We're both serious and intellectual but also get really excited about things like arcades and puppies....Took adventures to Brighton and Windor....Overall, it felt pretty effortless.
I really really like this dude and he really liked me too - it had most to do with our conversations I think, about having a mutual respect for each other's minds and thinking, and an unspoken agreement to give each other a lot of space. I don't think either of us needs a lot of affection or validation, so we expressed our affection mainly through spending time together and repaying favours of buying each other dinners and things like that. I think we both mainly need intellect, independence, and also excitement and progression, and had some kinky sex, drugs, and weekend excursions.
Looking back on it, I liked that man objectively more than maybe anyone I have before, but it did take me a while to warm up to him (I didn't have a good enough chance to thoroughly observe him before we started hanging out, so I was skeptical until after maybe a month and a half) - and I think that INTJs and INTPs are a great match. I also have close friends, a female INTP and male INTJ, who have been dating for a long time and are great friends and a great couple as well. They were close for a long time before they dated which I think is more typical, so I think just getting past the initial admission of attraction is probably the hardest part.