Well, Hyatts in general are great hotels. The Cambridge one is right on the Charles River and is a nice property. Being on the Cambridge side of the Charles makes no real difference in a city the size of Boston...unless you were planning on a walking tour of the "best of Boston"...if that's the case...you should stay either in the Copley Square area (close to Newbury Street and the Common), or in the Fanieul Hall/waterfront area area...but again, Boston is very compact geographically. Everything is really walking distance in a way. If you like mainstream hotels, there's a Westin in Copley square and a Marriott at Faneuil Hall.
However, when it's time to make the ship, no matter how close you think you are to the pier, give yourself plenty of time. Boston traffic can turn into a nightmare in the space of a few minutes...and the main artery through the center of town is under massive reconstruction.