Iwona's apartment is a very good choice for staying in Madrid. It has everything you need for a pleasant stay. It is very clean. The neighborhood is a safe one, very close to city center and to important tourist attractions. We haven't used public transportation, we just walked from apartment to city center.
Iwona is a very nice and understanding person, we managed to easily communicate even if she doesn't speak English.
You should definitely book this apartment if you plan a stay in Madrid!