It's a really big church. You think you know how big it is from the picture, which is of course why you are picking this location, but let me tell you, it is bigger. And the balcony is right under it. It's actually somewhat hard to do justice in words. It's incredible.
The rest of the apartment is fine. We were there in August and the AC worked well, which is basically the only other part that mattered. The kitchen is tiny, but I can't really imaging anyone coming to Florence and eating in.
I definitely recommend this place. There is a supermarket on the corner where you can pick up a reasonably-priced bottle of wine for the balcony. It's worth it.