We stayed here for 4 nights. Basically booked it because of the great reviews it got here.
And it did not disappoint: the hotel is truly at a great location; just a few blocks from the Karlsplatz subway station (main hub, goes to almost anything you'd wanna visit in Vienna).
It's also conveniently close to the city center (about a 5-10 minute walk). We actually walked to most things in the center: Stephansdom, Staatsoper, Majolikahaus, Secession, Hofburg, Ankeruhr...
It seemed like the room we got was a former appartment and it was huge. Bed, TV, couch, desk and some closetspace in the room, with the toilet & shower in a separate room down the hall (all within the "appartment", so private).
Breakfast was OK; bread, toast, sugarbread, tea, variety of cheese etc.
Staff was nice and all spoke English.
There was a supermarket right across the street, always handy to get some discount drinks & Mozart Kugeln.
Overall I'd recommend this hotel to anyone looking for a place to stay to conveniently discover Vienna; the location is just great and the price is perfect. The rooms are big & clean, though don't expect any flatscreen TV's or jacuzzi ; )