Salvatore is a great host! Though we haven't actually met him, he was always in touch by email, giving us helpful information about everything logistic. The flat was amazingly clean and tidy, with a nice bathroom and a nice brand new kitchen, and very nicely furbished. The position is great, the flat is truly a few steps away from the botanic garden and the Belvedere, you have trams at 2 minutes down the road, taking you to the city centre in 5 minutes, and trams going both to the Sud Bahnhof and Bus Station for Bratislava are on the main street under the flat; Rennweg station is very near if you're coming from Vienna airport.
We would totally recommend Salvatore's place to anyone visiting Vienna, the place is perfect for a couple!