We couldn't have asked for a better home base and a better host in Rome. Apartment was large and very well equipped. Three floor to ceiling balcony style doors open out to the street. Great for hanging out and people watching.
You can walk to all the major sites although I would suggest taking the metro to the Spagna stop if coming/going from the train station. 5 minute walk to Spanish Steps. 10-15 minutes to the Pantheon/Piazza Navona. 25 minutes to the Vatican. Travel maps, guide books, satellite tv, coffee, microwave, etc. It's all there at the apartment.
Our best meal in Italy was at the restaurant right downstairs (family owned, great food, nice people, not expensive - Taverna Ripetta). Gets great reviews.
On top of all that Antonino (your host) is the most attentive host I've dealt with on Airbnb. he will get back to you really quick with any questions or concerns. A real plus when you are traveling from overseas.
If we ever go back. We wouldn't hesitate to stay here again.