Ten friends and I rented this house for an end-of-June wedding in Williamstown and had a magnificent stay. The house was large, spotless, and comfortable, fully equipped with everything needed to grill, cook, and bake, as well as all the necessary linens. Several "family" spaces to enjoy. A very quick (c. 5 min) drive to the center of town, and just up the street from the Wild Oats food co-op. Venetia made everything, from check-in to check-out, so EASY.
The house indeed sleeps eleven, assuming three couples/pairs sleep in the upstairs king and queen and in the downstairs queen, and assuming the use of the downstairs pull-out couch. Some large groups might find it preferable to set up an air mattress on the main level (plenty of room for it and no other bedrooms there), so guests are more evenly spaced out throughout the house.
Hope to stay here again soon! Highly recommended!