I stayed with Jon during a Christmas reunion with my family (one couple from Seattle, one from Texas, and my wife and I visiting from Amsterdam). First, Jon's house is in an excellent location- there is plenty to do within walking distance (grocery stores, restaurants, and even the Barclay's center), plus the connection to public transport is outstanding- there are a few stops within a 5-10min walk, leaving you with tons of local / express train options. We traveled to Manhattan every day and never spent more than 30min on the train. Additionally, the house is huge and never felt small with six of us there. The kitchen is big enouch to cook a modest meal, and the dining / living rooms are perfect places for larger groups to reconnect after a day of activities. There's also two full bathrooms, so just a tiny bit of planning prevents any bathroom scheduling conflics.
The main thing that keeps this from being a perfect rental is the sleeping arrangements- there is really only one real bed suitable for two people. There's a second queen bed in the listing that can accommodate two people, but it's only a sofa-bed in the 2nd floor study (separated from the main bedroom by a curtain). The 3rd and 4th bedrooms on the 3rd floor have twin beds which, though more comfortable than the sofa-bed, will always feel like two separate beds even when pushed together. Families or groups with people desiring individual beds will be fine here (the top two bedrooms would be perfect for a few kids or friends bunking together to save money), but you if your party has more than one couple, you might consider other options.
All things considered, this property is a pretty good value- it's a huge place that can accommodate many people, and it's in a perfect location. However, if I were to return for a similar trip, I'd only consider a return visit if at least one more queen+ bed was added.