Well, this is a tough review since we unfortunately didn't have a great experience with the arrangement.
First the good: the location gets five stars since its right next to the Vatican and most key locations are walkable.
The bad: We were a group of 8 and the listing mentions this to be adjacent apartments - however, this is not the case. The two apartments are in two separate buildings - so that's two floors down and climbing two separate floors. This made is quite difficult for our group to coordinate/hang-out etc. Both apartments are kinda small and poorly configured. The amenities are poor at best.
The worst: Even prior to our arrival, the hosts were some what neurotic on our time of arrival. We understood since they had a flight to catch and arrived sharply at the discussed time. Upon arrival, they asked our group to split up into two so they husband/wife can orient our group to the apartment(s). Giuly was nervous on her tour - mainly focused on how it was important to turn off the A/C. Unfortunately, Paolo made my sister and sister-in-law very uncomfortable by being rude and asking them for their ID, etc. saying he can't give them the key unless they had proper ID. The group was split up hence the ID was stuck with one group. This should not have been a deal, since we were friendly and relaxed. However, we felt the hosts were very neurotic and rude in welcoming us.
We won't be staying here again and unfortunately won't be recommending this for anyone.