A very interesting question and answer.

My own feeling, and I don't mean this entirely facetiously, is that the trombone is a very difficult instrument to take seriously. It is just funny. (And the same applies to jazz trombone.) I have just been sent for review a CD of Dominick Argento's cantata Jonah and the whale, with an orchestra of three trombones, three percussion, piano, harp and organ. And one can't quite take the trombone music seriously.

For my money Berlioz is the only composer who made trombones really effective - whether wonderfully accompanying Mephistopheles in La damnation de Faust or the fabulous pedal notes in the Requiem (copied by Havergal Brian in his Gothic symphony).