Looking at all the type profiles (to compare with APS first, then to see where I fit second), I figured I was some kind of NP. (I knew the ENFJ I got on the Keirsey test online couldn't be me).
When I finally figured out the basic comparison between systems, that pointed to INTP. Looking at the profiles again in that light, it then made more sense. The profiles all emphasized the "detached analysis" more than anything else, and I didn't completely pick up the identification with it until then.
Then, I run into this hack "expert" who suggests ENFP based purely on me sharing ideas enthusiastically (Ne+Fi+Te). All of the aspects of the theory that were oversimplified (such as Ti=detached analysis; Fi="enthusiasm") were used for this. I did remember earlier on identifying with a few of the ENFP descriptions, and the Keirsey test actually had J and P tied at 5; but it otherwise seemed like a copy of the fellow Sanguine ESFP. (Not being familiar with the S/N dichotomy, and looking at it purely through expressiveness and responsiveness; I could hardly tell the difference between the two in descriptions!) So by the time I got that suggestion, I was surprised.
So then I began buying Berens, Nardi, Haas & Hunziker, and and these did help me solidify my type, though the function descriptions did leave ambiguities. A simulated Step II and the Nardi cognitive processes test also showed where I had some strong E, F or Fi traits.
When I finally found some Beebe articles, and learned more about Lenore Thomson's theory, then I finally got the hang of the whole function archetype theory, and it clearly fit INTP. Whatever Fi I "use" tends to fit the "demonic/transformative" complex. And it's not always about "using" a function, they are better described as perspectives, and they can remain "undifferentiated" outside the ego's normal preferred consciousness.