My partner and I were in Vienna for the weekend and we found Marian to be highly professional. They reached to us a few days in advance to let us know the check-in instructions, and remained available via phone call throughout our stay.
The place itself is clean and contains all the necessities for a weekend stay! However, we found the electronic lock, controlled by an app called Nuki, to be a bit troublesome. The app often had trouble connecting so it'd take around 5 minutes to enter the building.