The apartment is great; bright and quiet, with all the necessary items for a nice stay.
The only downside is that the wifi connection never really worked, but Riccardo has mentioned that he will be upgrading to a new provider soon, so hopefully that should fix things.
The location on the Guidecca island is nice (note that where airbnb has pinpointed the apartment is wrong; it is not on the "main" venice island), but you will need to take the free shuttle or the water bus to reach the sights.
The free shuttle comes frequently and is fast, but be aware than when going "home" you will have to queue or wait for the next one, as it gets busy on the way back from San Marco.