Many many thanks for the nice and detailed comment, Imag! I'd wish to have the background in exact focus too, along with the motion blur of the people, though. Next time I'll have to use the tripod there in order to be able to use a bit slower speed. But I have the impression that it is also overexposure of the lights at the depth that brough this kind of "softening".
Nick This is very good. I have been looking at all the pictures you posted today and they are extremely good. The background being slightly out of focus forces the attention to the main object and at the same time creates a sensation of movement. It works for me.