Christian's place is an excellent value. It's located in a multicultural neighborhood, with quick access to tram and metro stations (150m away) and quite close to the city center, Belvedere palace (you could even walk there!) and the Schönbrunner park.
Christian himself came to install a brand new washing machine for us! He's a wonderful host.
About the neighborhood, of course it may not be the most good-looking, but we walked the streets at night with my 7 month old daughter and felt perfecly safe.