My wife and I spent two months in Petra's apartment between late August and October, while we searched for a long-term apartment to rent in Vienna.
The apartment is in a quiet building, it's very large and roomy, and it receives a lot of light during the day. Also, it includes everything you need to feel at home. The building is in an excellent location, very close to the S-Bahn station at Rennweg, but not close enough that you can hear the trains. In fact, the location is so good, that we ended up renting an apartment very close nearby.
Petra has been very helpful and nice throughout our stay, always quick to answer our questions and to help. We would gladly stay in her apartment again!