Stephan,
last christmas I have seen the DVD together with my brother-in-law.
Result: Yes, the movie and its story have plenty of weaknesses and did not meet the high expectations.
However, the movie is not worse than any average Hollywood movie made for pure entertainment.
By the way, Thomas:
Destroying balloons with a flare was
not a mistake in this movie! The first German balloon hunter destroyed 2 balloons with his flare pistol in 1915. The first or one of the very first issues of the "Nachrichtenblatt" in 1917 reported a victory with a flare. As well I have a report about a British pilot who was killed when he tried to destroy a balloon with flares (after failed rocket and MG attacks). German ballon buster
Heinrich Gontermann reported about use of flares as well. The use of flares was a real option against balloons and not invented by the makers of the movie.