We stayed in the apartment end of July to spend 4 days in the city exploring the Biennale. The apartment is perfect if you want to spend most of your time exploring the main sites of the Biennale, but be aware that the apartment is quite a bit removed from the main sites of Venice - we chose the apartment for exactly those reasons.
The apartment is beautiful and very nicely decorated with nice little details. The only thing that really ruined the fun a bit is that the apartment gets SO HOT. The apartment only has two small fans and no air-conditioning of any kind, and the apartment was hotter then the outside even though we kept the blinds down all day. The apartment didn't really cool of until around midnight.
But if you visit the city outside the really hot summer days this apartment is very nice, and communication leading up to the stay was easy and very nice.