Some of the lecturers are wonderful and right on the ball with talking to children without sounding patronising. Others are not so good.
We used to watch it every year with our kids and always enjoyed it, though some more than others.
My other regular spot of science was the Faraday lectures, done by a different large company each year, on different subjects. That was a bit more grown-up, though still aimed at non-scientists (well, mostly undergraduates or graduates and their children) I remember one on coal, where they had a complete ginormous coal-boring machine on the stage of (I think.... ) the Assembly Hall in George Street - or may be it was the Usher Hall. Was anyone else there who could confirm this? Can't imagine how they got it in.