I stayed at Valeria's place for over a month during the Biennale. It's perfectly situated for this, being 5-10min walk from the Arsenale and 15-20min from the Giardini. Valeria was not present but easily contacted and solved any problems quickly. The flat is clean and comfortable and there's a good array of cooking utensils. There are also local shops and bars nearby which are very un-touristy. Recommended, especially for longer stays.