I have stayed at this Hilton many times over the years. I travel to Vienna for business, and the hotel is very conveniently located near public transportation and the inner city. The views from many of the rooms are spectacular.
There are several downsides to this Hilton, however. The staff are neither especially friendly nor efficient. The hotel management is focused on large (and lucrative) conferences, and not on individual business travelers or tourists. The breakfast offerings are good and plentiful, but the organization of the space is poor, and it difficult to navigate the buffet areas when the hotel is crowed, as it almost always is.
This hotel claims to be "very ecological." That's simply not true. The recent renovations tore out almost the entire interior fabric of the building, which was hugely wasteful. The hotel also overheats its rooms in winter.
The new decor is, even by large hotel chain standards, remarkably tasteless. The lobby looks like a giant American "fern bar" of the 1980s, and the "art" in the rooms and corridors is breathtakingly bad.
Puzzling, too, is that the restaurant is closed for dinner on Sundays, and lunch and dinner on Mondays. For me, as a longer-term guest, this very inconvenient. This is not at all to international standards.
The best thing about this hotel is its location. It couldn't be better. If the management just showed two grams of interest in ordinary travelers, the experience would be much improved.