Bernhardt received me in the probably craziest check-in he had but was kind and gave me tips. If you let him add you on whatsapp, he will also send these there. He answered quickly and the only time he didn't, it wasn't urgent.
The place is stylish and a little bigger than it seem on pictures, with nice shower and bed. The bathroom sink seemed a little clogged, but it was a small issue.
The big question: location. It is indeed well-connected (2 major lines are really close to the flat) but you will probably need to use public transportation everyday and, like everything in Vienna, it isn't cheap and devem with precise instructions from Bernhardt, I got lost. On the other side, you can eat and buy stuff near your lodging for a better price than in the central zone. I believe it can be a plus or a con depending on your travelling goals.
If I wanted to visit Vienna again, I'd consider it for a second time!