We thoroughly enjoyed our stay at Bernini House. It was a fantastic location, just a few mins walk to St Peter's Square and from here we found all of the other major sights of the city easily accessible by foot. However if you don't wish to walk, the 64 bus (which stops right outside the building) was a fantastic link through the city (and very cheap 4euro day pass, which you could buy from the tabacchi opposite the building) and the open top sight seeing buses all stopped at the end of the street leading up to St Peter's Square from the castle.
The apartment itself was very clean and spacious and had everything we needed. The host was very helpful and answered lots of our questions giving tips on where to eat etc. I would definitely stay here again and highly recommend this place to others.