[Would you mind telling in which areas things have improved? I stayed in December in a Park Suite and my stay, while uneventful, was nothing to write home about. I wish they'd manage the place better as it is the nicest hotel in Vienna from a hardware perspective.

Things have improved a TINY bit, I should have said. General attitude of the staff. Service was warmer, particularly in the restaurant. Saying that, I had a disastrous room-service experience - so bad it was almost comical and housekeeping missed evening turndown one night.
It's a stunning property that should be managed by Four Seasons not Hyatt.
Next time, I will try Sacher or go back to the rather good Sans-Souci.