Good for business, not good for families and romantic couples. The generosity, elegance and seamless service of Vienna's other 5-star hotels are NOT fully matched by Hilton Vienna Park. I can write more about this if you want to know the full details. Checkout (on a Saturday) took about 20 minutes of standing in line in the lobby: Awful experience. Late checkout at 15:00 instead of 12:00 would cost 2x45=90 EUR(!) extra for our two rooms, so we decided to check out early. The atmosphere in the lobby and bar is a bit stressful, very crowded and (annoying) electronic dance music is often played. For my taste, this does NOT feel elegant and upscale. I don't mind Hilton's motto: "Stay (pay) more - get more". However: Vienna's other 5-star properties have more charming ways of seducing us to spend more money. Hilton can learn a lot more about profit maximisation from their local "rivals".
NB: Don't book a room rate with breakfast if you want breakfast served in your room. That will actually cost 28 EUR per person - plus room service charge - EVEN when you have already paid for breakfast (It must be taken downstairs, in the crowded restaurant area).
The view of the Stadtpark and Cathedral from 10th floor and up is stunning! However: The "city view" on lower floors (standard rooms) is not good, some might actually find it depressing. And generally, the rooms are minimalistic, but clean. The bathrooms are a bit too small.