We have stayed in this flat for 4 days with a big family of 9 adults and 2 little kids and the flat comfortably accommodated all of us. The beds were comfortable and kitchens equipped really well. We travelled in quite a cold time of the year, so in case you do to be prepared to take thick socks with you or just walk in shoes in the flat.
Location is perfect, with Colosseum in 2 mins walk from the flat and 2 Metro stations nearby you can reach even furthest parts of the city in no time. As for all the main attractions (except Vatican) you will need only 10-15 minutes walk.