We had a great stay at Claudio's apartment with our two children. We had originally booked somewhere in a busy area near Piazza Navona which cancelled, but it turned out for the best. Claudio's place is in a smart area near the Vatican with a nice street of restaurants round the corner (Borgo Pio), 10 minutes from the Metro and within reach of many sites if you don't mind a bit of a walk across the river, which was fine in the pleasant October sunshine. The apartment is well decorated and has quiet Aircon units.
I had been a bit concerned about check-in since it needs to be done in person within a specific time frame, so a flight delay could add waiting charges, but it was fine in the end. I guess that on these larger apartment buildings a key locker outside would not be practical.