I dated an ISFP once and I was head over heels. An analogy that really illustrates the connection for me is if you were to imagine yourself in a foreign country where no one speaks your language and then you meet the one person out of an entire population that speaks your language. How would you feel, perhaps VERY understood. That was what the Fi/Fi connection felt like to me, before I knew about MBTI of couse, and without MBTI I figured "Welp, this person's my soulmate." We did bicker over small things though.
I also dated an INTJ girl and it was amazing to say the least. Long story short she spoiled the crap out of me with my favorite things lol. Once again it was a very Fi/Fi connection.