I upgraded in the hopes that some of the broken issues in PowerDVD 19 would be fixed, but the Blu-ray volume slider is still broken. Prior to version 19, Blu-ray disks played at whatever volume was set in the application, now they always play at maximum system volume and ignore the volume slider.
Standard DVDs do respond to the volume slider, but not Blu-ray discs. If upgrading doesn't provide any benefits then this will be my last.