We (4 adults) stayed at Frederic's place for 5 nights in 3rd week of April 2016. The location of the apartment is excellent - very close to the Colosseum, public transit and restaurants. It can comfortably sleep 4 adults. Kitchen is set up for basic cooking. Frederic is friendly and very prompt in responding to any questions.
If you are from the US here are some clarifications. Although the place is advertised as having a dryer - it is actually a clothes line - so you air dry clothes. The washer works very well. Frederic provided us with coffee powder, tea bags, and toast for breakfast. The internet signal was weak to nonexistent - so don't rely on it.
The place gives you a feel for what it's like to live in a typical Roman apartment; but beware It is an older building. So for example, the bath tub is high and hard to get into if you have any disabilities, or are older. Also the place could use some freshening up - older uncomfortable sofa and old blankets/linens.
Couple of suggestions - if you use the metro to come here, do not use the main Colosseo exit - there is another one that takes you through the back - easy to get to his place. Also familiarize yourself with the lights in the outside corridor and inside stairwell - you will definitely need these lights.