We stayed in Marco's apartament for 4 nights and we were 6 people.
At first, some advantages.
Location is good, if you are interested to go often to Vatican, it is really close. To reach old town, you should take transport, metro station is near home. Also, there is a 24h working grocery shop near. Apartament is spacious, enough space for 6 people to stay.
Now, what really got us down was late night check in fee, we came by late flight and the landlord wrote us that if we check in until midnight it is 30€ fee and after midnight - 50€ fee. We came on 00.08 and we had to pay 50€. That really got us down because in appartament discription was written that check in time is anytime after 3pm. So, that additional fee for your own guests is a really not good thing to do.
Now, about the showers. There is water heater/boiler, to get warm and not quick shower for 6 people was not enough warm water. Later we learned how to use water propertly, but still this is not good.
Cold floor, you should always wear something warmer.
Really hard to open a door and enter to the flat faster because of strange locks.
So all in all, we liked the apartament but those fees and comunication was just a business nothing warm and friendly.