Well Located, Undergoing Renovations
Stayed recently for a 2 night business trip. The Hyatt is on the edge of downtown within reasonable waking distance to most of the sights and destinations in Boston. I was able to easily walk to the Quincy Market and North End area for restaurants and Chinatown is a stone's throw from the hotel. The hotel is also very near the downtown crossing T station for other destinations.
Overall the service from staff was nice. My room was large and comfortable.
Downside at the moment is the lobby is undergoing renovations and feels somehow off. It is on the 3rd floor from street level so 2 elevators are required to access rooms. The fitness center was just OK and quite a hike from the elevators on the 6th floor. 
Not a bad stay but I'm not sure I'd stay here again.