I have just watched Harry Potter (1) at Dresden Kulturpalast and the score was played by Dresdner Philharmonie which is an amazing orchestra that I have heard a lot of times.
The music is fantastic and the orchestra was absolutely in line with the film. Especially the ending was very dramatic with this live music. The orchestra got a standing ovation at the end which very rare in classical concerts. But the audience was probably not the ordinary audience that visits classical concerts normally. In fact there were a lot of children in the audience what I think is great.
The music was relatively loud compared to the normal volume in the film. Therefore they switched on subtitles what was very helpful in some scenes.
Also the conductor asked the audience at the beginning to cheer whenever they felt like doing so. And we cheered a lot! The atmosphere was great.
So I enjoyed the event a lot. But do you need it and is it worth it? It is quite expensive. I had one of the best seats in the hall and that went for 97 euros. During most of the film I was not even aware that the music was played live because it fitted so seamless in the film.
Therefore I would say it was a good experience but I won’t probably do it again.