The apartment is small, but charming and recently renovated. It's on the ground floor but the street is very quiet so sleeping with an open window was no problem for us. It was very clean and fully equipped with what we needed for a few days' stay.
While it's not located directly in the center it's only 4 metro stations away from Wien Mitte (walking to the metro takes 10 minutes) and there are several tram and bus connections too.