Just dreadful.
It is appropriate that John Baxter called his critical/biographical book about Ken Russell "An Appalling Talent". Russell is certainly not without talent, what he frequently is, however is without a brain.
I have enjoyed many Russell films ... I think "The Devils" is a great film. I even enjoyed the over-the-top "Crimes of Passion, ("China Blue") and the even more over-the-top parodies "Lair of the White Worm" and "Salome's Last Dance", but there are limits.
"Mahler" clearly shows that what Russell needed was a big bully-boy producer standing over him with a whip to hold back his wilder excesses.
I can see where someone like Richard Strauss who was pilloried by Russell in "Dance of the Seven Veils" deserved being shafted, but what did Mahler, a far greater artist and human being do, to deserve this?
The film is so arch that it is hard to sit through. The dialogue is risible. The fantasy sequences more akin to Russell's obsessions than Mahler's.
If a Russell film ever contains a good performance, you can be sure it is because of what a good actor has extracted from the script, not because Russell has a clue how to direct them. Good actors give good performances, (Oliver Reed, Glenda Jackson, Alan Bates, Max Adrian), so-so actors give terrible performances, (examples to numerous to name here), but you'll find a lot of them in "Mahler".
The film lurches wildly between the arch and twee and the scatalogical and masturbatory.
Dustin Hoffmann predicted that if Russell were to direct his projected Mahler bio-pic, someone would come after him with an elephant gun. Perhaps someone should have. Mahler certainly deserved better.
But you ARE Blanche ... and I AM.