The place is spacious, clean and well-located, we had a great time in Vienna! The hosts were very helpful and quick with their reactions. Also, they supplied all things for toddlers: a pot, a baby bath tub, lots of books and toys. That was amazing!
The downside of the apartment is that the street, Josefstädter Straße, is quite noisy and busy. If you are sensitive with noise, I would suggest to bring ear plugs. Also with children, it was not always easy, as both during the day as well as in the evening / at night, it was either loud (windows open) or hot (windows closed). But that really is just a small side-note, apart from the noise – and perhaps the fact that the flat is very bright, which is amazing on the one hand, but sadly not on the other, if you have a toddler who wakes up at 5am to the daylight ;) – the Altbau flat is gorgeous and super well-located!
(For those traveling with children, there even is a small park with a playground behind the house!)