The facility tour guide made us feel very welcome, answered questions, and gave enough time at each place (you see three separate galleries overlooking the 747, 777, and 787 assembly lines). The scale of the place is huge.
The gallery is looking a bit tired, with several sections not working. The most interesting part is the Rolls Royce engine display, but that could have more details and information. The GE engine display is fairly pointless with no explanations.
Do visit the viewing deck - you need to use the elevator from the main lobby.
Also - the cafe is very basic and service rather slow - this could be improved.