This was our first AirBnB rental and we could not have been more pleased with everything.
The hosts are great communicators and very prompt. Their information was detailed and precise. They arranged transportation ahead of time for our family's arrival and departure at the Rome airport in Fiumicino.
The apartment was exactly as promised. Well, appointed with all of the small amenities you need from kitchen to bath to laundry. The balcony is great! It is almost at the center of the piazza on the second floor. The three french doors that open to the piazza can be opened to let in the cool morning air and bustling noises of the piazza or closed to quiet the crowds to a murmur. The guitar players playing for tips in the piazza serenade you almost the entire day.
The sleeping arrangements are flexible. Two of the bedrooms have queen beds and the middle bedroom may be a double or a queen, we didn't use that room but it is a bed that can sleep two regardless. The two couches in the living area are both pull out double beds. Sleeping 10 here is definitely possible but as others have noted, the single bathroom could be an issue with that many people. But as the hosts mention in other comments they are adding another bathroom which will make this place an even better choice for a group larger than 4 people.
We are planning on returning to Rome again next year and will be looking to reserve this apartment again.