I always thought it would be neat to do a theater tour in Europe.. always get to a few when we travel but having that as a focus would be fun .. might be a while though...It's pretty poor on the sides but it is excellent in the centre part of the stalls. Also it has steps, so the seats go slightly above level of the stage which I prefer, compared to being below the stage like in the lower section of Birmingham or concertgebouw.
Non box is fine, Sheldonian is the by far the best for acoustics. I haven't been to Berlin or Vienna though I have been to the Unter den Linden opera house in Berlin
Phil