The location of this house is just outstanding. It's right in the middle of everything- all the sights are not more that 10-15 minutes walk (yes, walk!) away, and that itself is wonderful. Add to that the fact that the area has great restaurants, and Piazza Novona is barely a couple of minutes away!
The house is very comfortable, and accommodates four people very well. The beds are comfortable, and the windows seal out the noise from the rather noisy restaurant downstairs very effectively. The bathroom is a bit small, and might be an issue is you are big built, but we are all small in my family, so it was fine for us.
Alessandro is an outstanding host. From helping with tips and questions before arrival, to helping take our bags up to the flat and done again when we left, to helping us find a shop to buy a new suitcase when one of ours gave up, to helping us sort transport when there was a strike threatened, he's always there. It's a pleasure to be in his house.
In sum, a great place to stay, great location, very comfortable. The only watchouts I can think of are the small bathroom, and the fact that it's on the third floor with no lift. If climbing stairs is an issue for you, then this house is not for you. Otherwise, go right ahead and stay here and enjoy your holiday !