Although Siu's place seems a bit far from the centre, it is just next to tram 37 which bring you to the city centre in 10 to 15 minutes. It is located in a residential area and you can find many gardens and green place nearby.
The double bed is comfortable and everything is very clean and well organised. The only small drawback is that the heater may not be warm enough for those coldest days in Vienna.
I would definitely recommend Siu's place for budget travellers.