Marco's place was clean and comfortable, only 400m or so from the Colosseum itself. This also happens to be the closest metro stop, which is essential for getting around the city. The next-door restaurant gives the block a lively feel, but otherwise the neighborhood is very quiet. However, beware: the hot water does not last very long! Try to take quick showers.
Marco and his friend who checked us in were extremely helpful, even leaving us a list of the best (non-tourist-trap) restaurants and sites to go to.
Also, be aware that checking is past 8pm comes with a fee. Overall, a convenient and comfortable stay!