We had an okay stay at Massimo's place.
Let me start with the good:
1. Location is great. You come out of your door and you're steps away from Trevi Fountain and lots and lots of shops and restaurants.
2. Massimo was responsive and offered timely advice and solutions throughout our stay.
3. Updated (though super tiny) bathroom and shower.
The bad:
1. Place is tiny! If you have full-size suitcases, you'll have next to no room to open them. There's barely room to turn around in there.
2. No AC. If it's hot, you'll need to keep the window open (which may or may not help) and hear lots and lots of street noise, because it's very crowded by the fountain.
3. We lost power twice because we plugged in our blow dryer. We had to, because the one in the room was incredibly cheap and inefficient. Wi-Fi connection was iffy.
4. We stayed for 2 nights and were provided 2 "bath" towels and two hand towels. Both were thin, kitchen-quality towels. When we asked for more, Massimo offered to have more brought over for extra 10 Euros. Not okay.
My advice:
If you really want to stay in the vicinity of Trevi Fountain, there's a hotel right next door to this place that charged less per night than we paid. If there's more than one of you and you have more than a small carry-on with you, I recommend you stay elsewhere.