I stayed at Amr's apartment for 2 weeks. While I did not meet Amr (as he was out of town) he was quick to respond to my emails prior to my stay; and organised for his friend Sebastian to meet me with the keys. Sebastian was very helpful during my stay and quick to sort out any problems (there was a slight problem with the heating, which was promptly resolved).
The apartment itself was small but very comfortable, with all the amenities I required for my 2 week stay.

With regards to location, the apartment is within walking distance to the U-Bahn and Westbahnhof, or about 40 minutes by foot from the Innere Stadt.

I would most definitely recommend Amr's apartment to others. I had a very pleasant stay and would love to stay again when i next return to Vienna.