georg's place is great! very central, very clean, very bright, opposite of a small park which means perfect privacy even without the curtains closed. rarely had such good host places to stay in. georg himself is as awesome as his place and will help you anything you need. visit him in his own bar just behind the opera house!
advice: when arriving by plane, take the s7 to praterstern and then the u2 to rathaus, it's a 30min ride for a 4,40 euro fare.