I don't have INTP best friend, but I do have several INTP friends.
INTPs are laid back people. They are nice and very accepting. They are funny, smart, and naturally mature. I make friends easily with INTPs. Our Te and Ti seems like a perfect match to each other.
What I don't like from INTPs are their laziness and inconsistency. ESTJs are people in action. We dislike broken promises and repeated mistakes. So if you can't keep your words, don't make any promise.
And some times they can be very deep into unimportant details that make them afraid to try new things or get sudden anger to the whole world. LOL.