All the arrival instructions were clear and accurate. The room itself was as described (good condition and convenient). Both the house manager and the host were extremely helpful and friendly. The only reason for four star rating was the house air conditioning system, which was programmed to shut down after business hours. It was hot outside during the day (30+ C /86+ F), so the room turned pretty warm. However, according to the host, the house manager changed the program later.
The location is very good, basically at the border with the 1st district, just steps away from the Schottentor subway station, and bus/tram lines. The building is behind Votiv church in a calm and pleasant area. The very heart of Vienna's old town (e.g. Stephansdom) is reachable by foot in about 15-20 minutes depending on your walking pace. There are a number of cafes and restaurants around.
To summarize, good apartment, friendly and helpful host and convenient location: recommended :)