Have to agree that Ni-dominants have the upper hand when reading motivations. INFJ's may have the upper hand over INTJ's, as their judging structures depend on social constructs (Fe) rather than logical ones (Te), though that might depend where the interests of either type might be, and how healthy they are. Unhealthy INFJ's have the tendency of becoming overly paranoid and suspicious if their Fe is not fed or developed properly.
On INTP's - hmm, no. Dated an INTP for a few months, and she could not understand me whatsoever. I could understand her very well, and predict her actions - even though she was being purposely unpredictable. This freaked her out a bit. From what I've read, they can understand interpersonal dynamics somewhat well - but other than that, not so much?
On ENFP's. My experience with ENFP's is that they tend to get a sense of someone's potential, and make seemingly random suggestions for that person. Sometimes it hits the mark, but more often it doesn't. One of my ENFP friends tried to set me up with a couple of her friends over a couple of years. Horrible matchmaker, though it resulted in some entertaining stories. Hmm, I wonder if that was by design... crafty ENFP's.
ESTP's can read people pretty well, I've found. Se is used for soaking up body language cues, and can be used for manipulative purposes, whether positive or negative for their target.