We stayed at Willy & Alina's place for 4 nights during the Easter school holidays. The apartment accommodated the 4 of us really well. The location was fantastic for the main tourist sites - The Colosseum is literally outside the door. Other major tourist sites (with the exception of perhaps the Vatican) are all within walking distance. Downstairs, there is a 24 hour supermarket (Carrefour) and some great family restaurants and gelateri within a block or two.
Willy was extremely helpful - always responding to queries quickly, as well as sorting out a taxi from the airport (with the fantastic driver Bruno - very efficient, punctual and entertaining!). Willy also put himself out for us on the last day by storing our bags after check out, so we could enjoy the city before going to the airport in the late afternoon.