My wife and I spent 5 nights at Stefano's Argentina apartment, which we'd highly recommend!
The location was perfect, with most of the attractions no more than 10 minutes away, and plenty of public transport close by for the Vatican when we didn't fancy the walk.
The apartment was as described, just like in the photos and full of little touches to aid our stay (usb and travel adapter, map, WiFi, etc). The kitchen was also well equipped, although we only used it for breakfast you could cook meals. At the end of a day's exploring it was nice to come back to and relax, certainly more than just a place to sleep.
Stefano's recommendations for restaurants and places to visit were spot on. We ate very well on this trip. :) There is a supermarket just around the corner, and plenty of places to eat within a few minutes walk. We enjoyed Alice pizza for lunch on the day we arrived, a quick but delicious option.
Would definitely stay here again when we come back to Rome.