Finally the root of the problem. Forget the zips and the whirly special effects. The casting of a woman in a male role completely changed the tone of the piece and it ended up not working at all. Mirren's performance was solid. But the ending was completely changed.
Prospero is a man full of anger, he tortures his enemies but in the end his heart softens thanks to seeing his daughter fall in love and so he does not kill, he forgives. This is a very strong character. He rose above his emotions and he found peace. Well done.
Prospera is a woman scorned, she tortures her enemies but in the end she forgives them. This is a very weak character. She is woman and so she could never really go through with it anyway, she did what all women do, she let her heart soften and she forgave them and gave up her magic, resigning herself to death.
In conclusion: Men and women are different and what may be a great strength in a man can be seen as a weakness in a woman. Helen Mirren should have killed those fuckers and the final shot should have been her on Caliban's shoulders waving her stick and cackling. Avenged.