I had an ISTJ friend, and I can just tell you my experience.
I say "had" because I moved, and we never kept in touch, but he was a good friend. It all started off as he was hitting on me, and it was the funniest thing

He'd pretend he would have some papers to write in the library during one of my all-nighters. Later he'd tell me that he had finished all his papers a long time ago, he just wanted to see me. He was so uptight and fidgety too, but he was funny.
He was so funny in general to me, and he never even meant to be. Like, he would make these little dishes with carrots and broccoli as a snack, neatly cut and arranged in like 8 X 8 little squares on the dish.
He was a health-nut, that's why the carrots

. He'd never eat any junk food, and would look at me like "eww" when I'd get a cookie. He'd also run all these marathons to help himself "focus on his goals".
He had all these borderline OCD things, I'd joke with him about it all the time. And he'd joke with me and my easy-goingness. It was all in a good-hearted way though.
He was irritated that I would go with un-ironed clothes, and that I was ALWAYS late everwhere. He bought me an ironer for me birthday. haha, no kidding.
I'd get irritated with his rigidity, uptightedness and unopenmindedness (pretty much to ANYthing), but I couldn't really stay mad at him. I just thought he was so funny in that way. He'd get grouchy when I'd do "out of the ordinary stuff", which I did pretty often, just to get him grouchy, cos I'm stubborn like that. He told me that he was also in a way, fascinated by it, even though he'd get grouchy sometimes.
He was always so "perfect", everywhere on time, all neat and orderly. He also had a ten year plan. He was going to grad school to become a lawyer, and now he probably works in this one lawyer firm, if everyting is going by his plan, which I'm 99% sure it is

. And he told me that he'd be a good husband to me, so he said that when he "settles down", and has enough money and a house and stuff, I could be his wife, and we could make little perfect babies. He said it as a joke, but there's truth in every joke, isn't there?

I told him, what the heck, I don't even know what I'm doing tomorrow!

I really have nothing bad to say about him, I had lots of respect for him. He was a very good-hearted guy.
So anyway, we were just friends, and it's different than romantic relationships. I couldn't imagine being in a romantic relationship with him, it would be so frickin weird. We'd get sick of each other, and I just know that he would try to change me sooner or later.
Ahh, I dunno if all this gibberish makes any sense or even is helpful.
But yea, I'm just generalizing here based on one example. So, I guess it all depends on what you like and what kinds of compromises are you and him willing to take.