Overall our stay in this apartment was more than good. The flat was very clean and had all the necessary accessories we needed. The guy that welcomed us (didn't remember his name :/ ) was really friendly. He showed where are the most important sights and how to get to them. The flat is located a little bit further from the city center than we expected (about 45-60 minutes by foot). But it is connected very well by tram. Number 9 goes directly to Vaclavske namesti, National Theatre or Ujezd street on Mala strana, where you can get on the funicular up to Petrin Hill.
To cut a long story short, I recommend Denisa & Petr's place to everyone looking for a clean and cozy flat in Prague for an affordable price.