True, but most of the incidents I've heard, the girl usually doesn't like having the guy's hands on her head...especially if she has little experience giving head.
And Kanashii, you're on the ball; the underside of the cock's tip is indeed very sensitive. Stimulated properly, that can make a man weak in the knees. On a few occasions I've had to stop the girl for a second so I could sit down and not fall on her (and I'm a bigger guy, so all my weight crashing down would be no bueno).
What you said about approaching climax is pretty spot-on as well. For me, though, the pulling and tightening is kind of a slow build-up; makes it feel like it's lasting longer, too. It may happen slowly for others, it may happen all at once. Everyone's different in that field.