Fabulous location. We stayed for 3 nights, and we were close to all of our planned activities (Kursalon, Spanish Riding School, Stephansplatz, great restaurants, and cafes). Quick access to many public transportation options (e.g., 10 min to Schonbrunn palace). 2 nearby grocery stores. I highly recommend the Italian restaurant Il Melograno, 50 meters from the apartment. Pricey, but totally worth it.
Apartment was basic but pleasant and charming. It had everything we needed for our short stay. My only complaint would be the shower -- the water heater kept turning off, so we had to turn it on to get the hot water. Also, the bathtub drain seemed clogged, so water would accumulate.