As advertised this apartment is in the best possible location. We found the best restaurants and shops just around the corner on the small street that leads to Piazza Navona. In particular the Fridgidarium was the best gelato we found anywhere and "Two Sizes" has the best Tiramisu probably on the planet. If you are on a diet then best keep walking past those.
The Vatican was an easy 20 minute walk. The Colosseum about 30-35 minutes, though I recommend getting a taxi there as the taxi stand is just at the end of the street and the Colosseum and Roman Forum is a lot of walking anyway. The Pantheon was about 10 minutes walk, and Trevi fountain about 20. All of the walks were through the lovely old streets of Rome and we found many random things to look at whilst going from A to B.
The apartment itself was lovely and comfortable, with many nice decorative touches (paintings/prints, trompe l'oeil etc). The housekeeper was very welcoming and helpful.
All in all we had a great few days and were sad to leave.