The first pass was at 18:48 local time (CET) in very deep twilight, with the sun only 4 degrees under the horizon. This meant the sky was still bright blue. A crescent moon was visible (with the ISS passing only a few degrees away from it), but almost no stars.
Nevertheless both ISS and STS-133 were well visible by the naked eye around culmination: the Shuttle was about 5 to 6 degrees in front of the ISS and slightly fainter.
A second pass, this time in a dark sky, was on an extremely low elevation of 12 degrees at 19:25:30 UTC. Yet due to the very clear sky, they were well visible by the naked eye again, truely at rooftop level:
In the image, the two trails overlap at their ends, creating one long trail. A difference in brightness shows where the ISS trail ends.
The Shuttle and ISS were 7.27 seconds apart, at a distance of 2.5 degrees, with the Shuttle leading. This corresponds to 54.5 km separation in reality.
At the deep twilight passage, I used my Canon EOS 450D, laptop and "EOS Camera Movie Record" software to record a short movie (below), showing the crescent moon and the ISS passing near it, low in the west. The Shuttle was still too faint to be seen at that time, brightening to naked eye brightness only when it was closer to culmination.