I stayed at Maria Cristina's home for roughly a month. I permatravel so I'm very accustomed to spending long term stays in airbnbs. Overall I had a great time. Maria and Adriano are such nice people.
I would say Maria's home is perfectly accurate to the description, incredibly clean, and therefore, very much deserves a five star review. The neighborhood is amazing, full of delicious restaurants (Dar Poeta and le levain have some of the best food I've had in my life), and I can confirm that the air conditioner works very well for the size of the apartment. Bed is very comfortable. The interior is just as beautiful in person. The internet is among the best I've had in all of my airbnbs. This is clearly someone's apartment they're sharing and not just a makeshift hotel room. That being said, if you are a big person, you may have some troubles in the apartment.
The only critique that I could offer is that your comfort in the space will really depend on your size. It is very small, especially by American standards. As someone who is 6'4, 235lbs I couldn't bend over to wash my feet in the shower, the shower was just too small for someone like myself. The sinks are only about 2ft off the ground so if you're really tall you need to really bend over to use them. I hit my head on the top of the shower and on the water heater pretty frequently. The apartment doesn't get overwhelmingly hot but it is exceedingly humid, so, the air conditioner is really necessary to be comfortable. The AC died on my second to last day and I couldn't stay in the apartment for more than an hour or two. However, given how long I was there for, 2 days wasn't a big deal. Finding a trash can is a bit of a challenge in the neighborhood.
I think if you're a traveler looking to get into the best neighborhood to sightsee for a week or two, this is an amazing apartment. If you happen to be very heavy, or extremely tall, this apartment might get uncomfortable, especially if you stay long term. If you're of an average size I'd say don't hesitate, it's a great space for you and you'll have an amazing time in Rome.