I highly recommend Mario's place! Me and my husband stayed there in the last days of May and we really enjoyed everything.
Here is what we loved about it:

1. ATMOSPHERE. It has a unique artistic atmosphere, very cozy and intimate, very relaxing, everything is arranged with a lot of taste, as you can see from the photos. it is nothing like being in a hotel. Even the bathroom is a piece of art. We immediately felt at home.

2. FACILITIES. Mario is a great host. He has provided us with absolutely everything we needed for our stay. We used practically all premises and facilities - not only the bedroom, but also the living room, the balkony and the kitchen. There is also free internet available.

3. LOCATION. The apartment is located in a nice resident quarter, in a contemporary Italian neighborhood - very green, calm and charming. Outside there is a big garden with lots of trees and you can hear nightingales in the dark. It was fantastic! You can buy Italian food, wine and vegetables from the near-by little stores. Unlike the most touristic places and Termini, you can see how this place is very quite and tranquil.

4. TRANSPORT. It is easy to get there - although it seems a little far from the center of Rome, you can get there in 10 minutes with the metro - at Termini get the line B to Monti Tiburtini station. The first metro starts in 5.30 am and the last is in 11.30 pm for Line B.
NB. Mind that Line A closes in 9 pm, because there is construction going on.

In two words - it is a lovely place!