Stefan's place is 8 minute walk from the Hofburg, where most of the balls are. 2-3 minute walk from the Museum Quartier, the Natural history museum, and more. 10-12 minute walk from Cafe Landtman (where Sigmund Freud used to hang out.) 5 minute from Nachsmarkt. Location wise his place is unbeatable. All the tourist shops, restaurants, things to see, and metro stops are close by.
Using his studio was equally convenient since everything is electronic, so no hassle of tracking/losing keys.
Stefan went out of his way to help me receive a wallet I had lost on a prior leg of my trip. He also spent time to help me connect to Wifi. He went out of his way on multiple occasions.