I spent 2 weeks researching hotels and am so glad I did because I was delighted by the experience and bang for my buck!
First, the quality standards are great. Second, the room was spacious and much larger than that noted by other competing 4-star hotels in the same price range. My room had large windows and faced the garden. The furnishing, flooring, etc., were clean and felt like it was new/well maintained, and looked splendid/well designed. The hotel has a wellness center (free to use).
Third, the hotel has a wonderful location - just 3 to 4 minutes walking distance to both the Rennweg tram and metro train station. The Rennweg metro itself is just a 4 minute train ride to the main Vienna Hauptbahnhof train station. One can even take the metro train to the airport from the Rennweg station. The hotel is 3 minutes walking distance to the Lower Belvedere entrance and from there it takes about 5 minutes walking distance to go to Upper Belvedere. The tram ride from Rennweg station to the central part of Vienna takes 7 minutes. Next to the Rennweg station, there are several cafes/restaurants/fast food options as well as a supermarket.
Additionally, I liked the small extra touches - for instance, the fruit and cool drink available at the reception and, as a green initiative, the option of receiving bar coupons for waiving room service. Finally, it's the outstanding value that the hotel offers (quality relative to price) that makes it a superb choice.