We loved our stay at Karin's place! It is just as described, has everything you might need and is located in a lovely spot right in a small park, with no streets, cars or noise.
The neighbourhood is very peaceful, has little shops and cafes all around.
The apartment being 2-3 mins away from the central station is very convenient for reaching the airport quickly, as well as all metro stations you need to get around the city if you don't want to take a walk.
After exploring the city I must say it is absolutely the best place to stay in Vienna, if we travel there again we'll be staying at Karin's for sure :)
Karin is a good host, the communication was very quick and easy.
In short words - I highly recommend that you stay at Karin's if you travel to Vienna!