I'm an INFP and I had a friend who was an ENTP I think the main problem was that he was just incredibly distracted all of the time, that unavailability was a rough spot, I take accountability for this too. Perhaps it wouldn't have been as much of an obstacle had I been more aggressive in trying to make the friendship work and being more extroverted when dealing with him and his schedule. But that being said it was hard to get a hold of him.
There were times when we had really good conversations, really thought provoking stuff about religion, scientific conversations about dimensions, relationships, etc. But I notice it was all rather random and all of these conversations happened at parties or random meetings around campus, nothing was ever planned. I kind of wanted something more concrete. In that matter I was always the one who had to extend myself and put myself out there and there were times when I felt rejected (which may just be my over sensitivity). But there were other times when he just disappeared and brushed off plans that were made. There was this one time when we were supposed to go to a party for my birthday that really hurt. But I hear that my be a common problem on the ENTP side.
There were times when I felt criticized just because I was unable to read him and I didn't understand the way he would communicate towards me, we actually got into an argument about that. I think that may have strained our communication because I often at times felt he was angry with me (when he probably wasn't) and I was under an impression that he didn't like me or didn't want me around, which is a problem with the INFP personality. So in that regard I can see how the power play comes in that was talked about in previous posts.
I always felt that he had all of the power in our friendship. I eventually stopped talking to him due to the power imbalance I felt. But there were a lot of good moments in our relationship as well. I remember there was one time when I had to go to the emergency room and he was there threw it all making jokes, he was with me in the room and I was extremely grateful for that, that's one of the reasons I tried for so long towards the end.