I've been there last week with my wife and a friend: We spent 5 days and we are fully satisfied of our choice.
The location is very good: it's quite as if it were in the country, with no traffic noise at all, but at the same time it takes less than 30 minutes to reach the very centre of town, thanks to buses, tramways and U1 line. If you arrive by car, you may leave it parked in the internal big yard and forget it as long as you stay in Wien.
When one gets tired of downtown, near the Pension may find a lot of inns and reastaurants with a pleasant country mood.
Sylvia and Josef, the owners, are very nice people, they give their guests all the pieces of information they need for their staying in Wien, and give they also a rich breakfast.
It's also pleasant to sit for a while at the tables in the courtyard under the trees, for reading a book, using wi-fi computer connection, playing cards, drinking a glass of local wine...
For us, next time to Wien will mean next time to Pension Wieselthaler