My niece and I were extremely happy with this apartment and our hosts Ruggero and Roberto. We were allowed to check in early and when my luggage didn't make it to Rome, Roberto called the airline several times and arranged to have my suitcase delivered to his home. He then delivered it to me late Sunday night. What could have been a terrible situation was turned into no big deal. Roberto went above and beyond. Also, he arranged a driver to pick us up at the airport (and the driver waited hours while we filled out the paperwork), and also a driver to take us back.
The apartment itself was lovely-high ceilings, spacious rooms, great balcony, comfortable furniture, well-equipped kitchen. We felt right at home.
The neighborhood is great. Right around the corner is the Spanish Steps and as everyone has pointed out, you are moments from all the other tourist spots. The street itself is more quiet and once you close the windows, you don't hear anything.
I recommend the Grotte restaurant (near Life restaurant--it has the orange vertical "Pizzeria" neon sign). We ate there a lot and the menu is varied, reasonably priced and the food is awesome! Our favorite spot for gelato was around the corner at Blue Ice on Via dei Due Maccelli.
I had an opportunity to meet Ruggero and both he and Roberto were very generous with their time, giving us info about Rome.

I highly recommend staying here and I will come back again to this apartment!