The main trouble with Fi is that its conglomeration of intriguing characteristics (whether good or bad) continue to warrant threads on it, even after the subject has been bludgeoned to a bloody pulp.
Seriously, aren't you guys getting sick of all these threads with "Fi" in the title that invariably snowball into a J-function showdown?
Sort of. I mean, I can't feel guilty about dogging on other functions if Fi has gotten its turn.
The main problem with Fi is that every description out there fails to capture what it's really about, because it's very hard to describe what it means. It's difficult to pin down, which in turn makes it difficult to analyze or talk about in a meaningful and direct way. We can shine a bunch of different lights on it, look at the shadows it casts, and extrapolate some characteristics of it from there, but we can't do much else.
Contrast this to Te, which Lenore indicates is pretty much exactly the opposite--it's insanely simple, which is part of its effectiveness.