We enjoyed our stay in this apartment; everything was clean and we had everything we needed. Rita (who met and let us into the apartment at 22:30) and Nuccia were both very helpful, answering our queries quickly and patiently. It is very near all the main attractions and good restaurants; Plazzo Conte Frederico was definitely our favourite tour and it's right opposite the apartment front door so it couldn’t be more convenient (but you need to walk around the block to get to the entrance).
We hired a car for the second half of our stay and Nuccia's suggested car parking at Piazza Alessandro Vanni worked out well as we managed to get the last car park each evening (although marked as free parking there is an attendant who will request payment to look after your car). We did buy ZTL day passes just to be on the safe side but note that the system of sending a text to activate a pass will not send an acknowledgment back if you are using a non-Italian phone number as it doesn't add the correct international prefix when replying. Apparently this is a frequent query, and cause for concern, in the tourist information offices.