Cristina's place was a great location to all the major sites, 3 mins walk from Uffizi and 10 mins walk from Duomo. We felt like we were right in the center of it all! There was five of us staying in the apartment which was a little tight at times but we managed as most of the time we were out and about exploring. Loads of restaurants walking distance away and the train station San Maria Novella was about 10 mins by taxi which was ideal as we did a day trip to Pisa.
The one negative was if you stay in the master bedroom facing the street you maybe disturbed in the early hours of the morning by the locals and tourist staggering home from a night out. I overcame this by putting cotton wool/ear plug in this really did help! I realise this is not Christina's fault but it's worth knowing and I wouldn't use this as a reason not to stay as the apartment and location is great!