Roberto's place is well located, it is clean and my parents and I had good time there. It is close to the train station but keep in mind that you need to cross 6 bridges to get there so with lugage it takes more time that Google suggest, but it is a problem of any apartment in Venice, so general suggestion would be to travel light. More about the appartment I can say it is both near the centre and at the same time not very crowded during the night which means more quite than sanmarco which is a plus in my opinion. In sum we had a good time in Venice and Roberto's appartment