Plamen is a great host, and we had quick responses to all our questions while staying with him.
Short summary: Great place to stay and explore Vienna!
Location/transport: Close to Praterstern train station; you can go straight from the airport to the apartment in around 35 minutes or less with public transport - convenient and cheap. Also close to the U1 subway line, which takes you to Mitte in 2-3 stops (around 10 minutes riding time) - another bonus! There are also grocery stores close by, and at the nearby Praterstern station there is even one that is open on Sundays (not common in Vienna).
The apartment is surprisingly big, and quite well kept. There is plenty of light through the vindows, and the closed balcony (unsure of the English for this, sorry) is a great place to dry your clothes.
Bring/buy your own: wine/bottle opener