The floor of our room (#2) dropped down 5 inches right after opening the room door, and the bathroom was 5 inches up from the bedroom: be careful while walking in dark.
We stayed at Residence Regola for 5 nights in May, 2015. It is well located, very near Ponte Sisto and Campo de'Fiori. Piazza Navona is short distance away. From P. Navona one can walk to the Pantheon area very easily. One can also visit the Trastevere area in 5 min. by crossing Ponte Sisto. There are many restaurants near the Residence (including Trastevere). All rooms are either on the 2nd or the 3rd floor, but one can use their elevator. Its location can be hard to find first time (contact them by email or phone ahead of time). The breakfast consisted of cold cuts of hams and cheeses, cereals, yogurt, bread, fruits, juices, milk, and some sweets. We enjoyed cappuccino every morning. Our room (#2) faced to Via di San Paolo alla Regola, but we had no problem with street noise (not annoying). The staff (Mariana, Valentino) whom we saw in the office/breakfast room everyday were very friendly and helpful. (For the day we had to leave early in the morning, they prepared us with bags of breakfast in the afternoon the day before.) The room was cleaned every day, but we had to request a new set of towels after 3 days of stay. We could hear some voices from other rooms, but we had no problem sleeping. The beds in our room were comfortable. The wi-fi connection in the room worked well. The room was equipped with an electric pot (with coffee and teas) and a small refrigerator. We used their computer to print our flight boarding passes. There is no Metro station nearby: One can find many bus stops not very far from the Residence: along the Tevere (Tiber) river, on Corso Vittorio Emanuele II, and Via Arenula. We often walked to Largo di Torre Argentina to catch the buses #40 and #H.