I know one other INFP, that I know of. She's one of my best friends. She's a lot more mature than me, even though she's only 1 year older... I find myself going to her for advice a lot. She's like an older sister, which is something I've never had since I'm the eldest.
And like other people have said, there's the whole instant understanding/effortless communication thing going on. I remember one of the first days I had been around her. We met because we went to the same college, and we were in the same dance piece for a faculty-choreographed concert. I go to the first rehearsal and find out it's a piece consisting of 4 solos. I was a freshman, with no solo experience, and I was so nervous I wanted to die. She comes up to me, put her hands on my shoulders, and says, "Don't be nervous." Most people don't pick up on my anxiety, because I'm very good at hiding it. But she knew.
It's also nice that we have the same weaknesses and struggles. It's nice to know that someone else is going through what I'm going through and GETS it. I can talk to her about absolutely anything. And we both understand each other's strange sense of humor.
So, yeah. If all the other INFPs are even somewhat similar to her, they're okay in my book.