How long off the boil, and whether it matters

I tried brewing the same light roast at three points after the kettle clicked off, measuring the water with a cheap probe thermometer each time.

Straight off the boil the cup was harsh at the edges. Thirty seconds later it was clearly sweeter. After two minutes it had gone a little sour, but not by nearly as much as the forums had led me to believe.

For darker roasts I could not reliably tell any of the three apart, which I suspect is the more useful finding.