First of all Angelo is an amazing host - he organised shuttle for us, baby crib, all that we really needed was there. He is also very polite and responsive guy - it's big advantage of renting his flat!
On the flat itself: It's very big and nice furnitured, located in quit area, but at the same time perfectly connected. Few minutes to main train station, few metro/underground stations just few minutes walk. We didn't mind walking so we walked up to Colloseum (15 minutes), Vatican City (45 minutes) and others (in 1 hour walking there is whole historical/touristic part of the city).
There is also elevator which is additional bonus if you travel with kids.
The only negative thing was noise from the neighbours - flat is in old building with very poor isolation, you can really hear neighbs talking, watching TV until late night hours every day (2-3AM). It was not big problem for us as we don't have troubles with sleep, but it might be for one.
At the end it's center of Italy and I would not expect anything different :)