My friend and I had a great stay at Petra's! She is a very friendly host and was always quick to respond to any questions that we had.
As mentioned by Petra and previous reviewers, the staircases can be a challenge. It would be best if you pack as light as possible. If worst comes to worst and you forget something at home, there is a shelf with extra toiletries, towels, sheets, etc.
The place itself is very clean. I loved the location: it's a short ride to the city center by tram 4, but it's in a quiet enough neighborhood that getting a good nights' rest won't be an issue.
If you want your stay to be less touristy and more like the life of a local, this is the place to be.