Paolo is a friendly and charming host and this is a terrific location for a very good price in a vibrant area of Rome. As other people have indicated, it can be very noisy (but only on Fri/Sat nights). However, this isn't from within the apartment complex but the surrounding area and really that's just Trastevere. It's a really, really lively area.
The flat itself was fine; clean with a really comfortable bed (which is a bonus after all the walking you will be doing). Tons of hot water and a kettle for those tea drinkers amongst you. Some people have said because it's a basement flat it's a little dark but for us it simply wasn't an issue as we were never back before nightfall!
What could be better? One main gripe, there is a sofa on the photographs which has been removed; consequently there is no comfortable seating downstairs. It's not a deal breaker but would have been nice.