I stayed at Guido's apartment for four days (three nights) in late May 2013, and in terms of its layout, cleanliness and location (below the Arno river and therefore the tourist-heavy city center though still within striking distance of the main attractions), the apartment was excellent. Guido was great too; very friendly, very accommodating. He sent me an SMS on my second day to make sure everything was fine. The only rub during my stay was the internet, which evidently for technical reasons was prohibitively slow. Guido, however, was apologetic, and on my last day in Florence he showed up with new equipment. I don't doubt that the internet is fast as lightening now. All this is to say that Guido is attentive. I recommend his place.