I've recently returned from a long weekend at the apartment, and must say that the reviews I'd seen had made me slightly apprehensive on arrival. However, a lot of issues raised by previous reviewers proved not to be a problem at all (the individual numbers of each apartment are there, but just are quite small and above each door!). In terms of location, the flat was perfect for us. A street away from overlooking the lovely Danube Canal (not to be mistaken with the Danube proper!) on one side, and a 15-20 minute walk into the centre of Vienna on the other. If you didn't feel like walking - although Vienna really is a city to explore by foot, if feasible - the nearest metro station is a 5-minute walk away, and gets you quickly into town. There's plenty of local supermarkets (including a couple of Billa's) and restaurants to choose from, if you did prefer to stay local.
That's not to say that everything was perfect either. The one message I sent to Harry weeks before arriving was never seen or responded to, which left me with some unaddressed questions when it came to checking in (fortunately all was very straightforward in the end, but I got the impression that if we had needed to communicate with the host, we may have struggled). Although the apartment is generally lovely and practically-furnished, there was a large crack in the glass kitchen door that you could potentially cut yourself on if not careful, and some partly-exposed wiring in the kitchen (both of these things I believe have been mentioned before), but these are anomalous issues throughout the apartment which, otherwise, we found to be clean, well-furnished and perfect for a long weekend away.