In it's most common sense (to me), it's just a quick shift in course.. a sort of "Oh shit!" switch, that makes me cover my tracks ahead of time. A perception of future development, but not something informed by Se exactly.
Just to illustrate, if you see a scene in a crime movie where a robber dispenses of a gun in a good way where it's bound to not be found, or sets up an obstacle to prevent pursuit - even if he hasn't seen his pursuers.. something that helps you take care of a problem before it gets worse. It's hard to describe.. I think any SPs will know the gist of what I mean though.
That description floating around of "gut feeling" in SPs kind of describes the understated nature of it, but I don't think it's necessarily from the "gut". More like a flash of insight. I think my philosophical side is still mostly judgement based, rather than perception based. If I get too caught up in perception, I personally don't think I'm stable. It's like Mel Gibson in Conspiracy Theory. lol. My Ti side doesn't tolerate that shit.. I want to slap myself out of it sometimes. It's too irrational. In one book, I read that ESP's Ni can come in the form paranoid jealousy.. like some sudden thought that your girlfriend is sleeping around, just because she didn't show up at time. Prolonged ISP ni wouldn't be much better off. If I was a strong Ni user, I would be an INTJ or INFJ. But I'm not.