I would definitely recommend Nicola's place.
The room I stayed in was as I expected. Nicole was extremely welcoming, friendly and full of useful tips on the city. She made my stay a lot more pleasant and did an exceptional job of hosting.
The apartment is extremely central too. It is approximately 10-12 minutes walk to the central station and Tivoli. It also appears to be in a nice neighbourhood. There is a lot of activity, restaurants and bars in the vicinity making it feel safe even late at night.