My wife and I loved this apartment! It had everything we needed and the quiet and comfortable.
It was just about a 10 minute walk from St. Peter's and a train station and about a 15 minute walk to the nearest Subway.
We didn't get to see a lot of Rome while we were there, but this area seemed to be just outside of the tourist trap that's around the Vatican. There were quite a fee locals in the cafe across the street. Actually, we may have been the only tourists.
I would definitely recommend this apartment if the Vatican is going to be the primary reason you're in the city. If its for ancient Rome, I might stay somewhere closer to there.