I've just seen the ISS for the first time. We realised it was due to go over, so popped outside. Lovely clear evening. Bright light in the sky. Is that it? Or is it that one below it? It's the one below: it's moving! Wait, there's another one next to it, also moving! That can't be right. No, it's the bright one that's moving!
It was a very peculiar optical illusion, making the bright light seem to be still in the sky, and the fainter one seem to be moving. After the few seconds of confusion, we watched the bright light move overhead. It whipped overhead quite fast, covering half the sky in a few minutes. It was very bright, probably about magnitude -3. As it got closer to the horizon, it dimmed and brightened a few times, then disappeared.
Observing astronomical stuff is cool. But watching the ISS was quite a different feeling -- people did that! A whole other level of cool.