I stayed at Grand Ferdinand for three nights. The hotel is located very conveniently in the heart of Vienna, with all important metro and tram lines close by. It is also just a short walk to major tourist attractions like Staatsoper, Karlskirche, and Stephansdom.
When I arrived at Grand Ferdinand, I was pleasantly surprised to be offered a free upgrade to a private room although I had booked a bed in the dorm room. Staying at such a beautiful and central hotel for a mere €30 a night can only described as great value. The hotel was perfectly clean and exactly as described. The staff was very welcoming and did everything they could to make my stay a wonderful experience. Even though I was only a traveller with a limited budget, I was treated just like a regular guest in one of the more expensive rooms and suites. Since I did not stay in the dorm rooms in the end, I cannot say what they are like, but based on the hotel's overall quality I can only imagine that you would definitely get your money's worth.
I myself am extremely glad I found this magnificent hotel via Airbnb and I will definitely stay here again if I ever come back to Vienna.