I went to an Eurotrip with a friend and we stayed in four apartments through AirBnB (Paris, Florence, Rome and London) and by far Mario's place was the best one.
Mario is the most polite person and very kind and helpful as well.
Unfortunately he had a trip scheduled on the same days that we stayed at his place, so we never had the chance to get to know each other better, but I'd definately stay in his place again when I'm in Rome.