Guest House Piazza Navona can only be recommended. Very well situated in the middle of everything, walking distance to many of the places you would want to visit as a tourist. And a taxirank close by :-)
The flat is very nice, clean and cosy. The bed in the bedroom is very, very nice. We were five adults and all of us slept well - one at the couch in the livingroom. The diningtable is too small for five - but there a so many great places to eat in the neighbourhood, so we didnt need it :-)
Massimo and MGPgroup is very easy to communicate with. They are very, very nice and helpful. I will come back here when I come back to Rome :-)