Stayed at the Imperial last September (the 7th-9th- the last days of a different era).
As a gold on a free weekend I was given a large room with twin beds and a nice view. The blinds on the window were motorized- a surprise. Large bathroom with shower and tub.
They had slippers (embroidered with "Hotel Imperial- Wien") and I assume that they had bathrobes, too, but I don't specifically recall.
Only "problem" was that I didn't notice that even local calls were ~ 1 EURO a minute and ran up a huge phone bill using my modem.