We had a lovely time at Nicola's place! The flat is exactly as described: small but with comfortable and enough space for two people. The balcony is fantastic! We had plenty of sunshine during our stay and pleasant temperature so were able to enjoy the lovely view. A tip: leave the blinds open before going to sleep and, if sunny, you will wake up with an amazing sunrise :). The apartment is based on the fourth floor and there is no lift but, after all the carbohydrates consumed during the day, the extra exercise was actually welcomed.
We also enjoyed very much the local area. Nicola's guidebook was very handy. We had a delicious dinner at La Caraffa (great for pasta and seafood dishes), fun at the L'Asino Che Vola (friendly community bar with local and nice bands/live music) and bought a beautiful mouth-watering cake at the Mariani Caffetteria (friendly family business - Via G. Capponi, 150).
Carrefour supermarket and small local shops selling fruits, vegetables and other amenities are located very close to the apartment. Everything was within a 5-minute walk, including the bus stop and Furio Camillo train station, which took us to the main tourist attractions in Rome (the ticket costs €1.50 each way and can be used for either bus or train).
In a nutshell, Nicola was very helpful throughout and the place was wonderful - we highly recommend it!