We stayed for 5 days in Emilia's apartment. It is so close to the metro, only 3 stations from Termini. Emilia was incredibly helpful and allowed us to check in at 1pm. The apartment is just great, very stilish, two big bedrooms with separate bathrooms. It was sparkling clean and it has a nice view of the Basilica di San Giovanni in Laterano. If you keep your window open it might be a little bit loud from the Metro C construction just outside, but since we left the apartment pretty early in the morning we didn't have any problems with this matter.
The apartment just got everything you could think of - even a washing machine and a dishwasher, which you won't find that easily elsewhere.
I deeply recommend staying at Emilia's if you want a clean, beautiful, spacious and close to the metro accommodation.