The apartment is quiet, very spacious. The kitchen has lots of various utensils. The host replies very fast and gave us different tips (we went to Osteria da Fortunata and really enjoyed it, thank you). The only complaint is about the internet, it's very slow (but it works :)
There's a supermarket in just 1-2 minutes walk from the house.
We tried different means of transport to get to the city center. Bus 81 goes as far as the Vatican , past the Colosseum. Trams 5 and 14 go to Termini. Very convenient. But in the evening the bus takes way too long, I would recommend to go by metro to Pigneto station and take a 5 minute walk (there are some nice cafes on the way). It's so much faster even though you may have to change metro lines.
All in all it's a very good place to stay. Thanks a lot.