Beautiful place. Excellent breakfast (and not expensive); highly recommended. We had a two-bedroom apartment (double/doubel). The rooms were larger than expected and it has a large common area and even larger bathroom.
The location is great, very close to the main attractions (St. Stephen's Cathedral, Opera House, Hofburg palace, etc).
The only negative issue was the lack of air conditioner. We got extremely hot days (92-93 maximum) and the nights were a little uncomfortable (the provided fans, though). I understand that we had an unusual heat wave, so perhaps A/C is not needed more than few days a year, but we encountered these days.