To answer the original question, I dislike the location of the Cambridge Hyatt: in a wonderfully compact city, this hotel manages to be close to exactly nothing (except the river, if you happen to have a kayak in your suitcase).

I would certainly agree that the Charles Hotel (Harvard Sq) is a great location, same for the Westin/Mariott/Sheraton/Hilton/Fairmont properties in the Copley/Prudential area.

The Meridien is a lovely hotel in a wonderful old building, but its location in the middle of the financial district is not perticularly good for weekend leisure travel.

The Beacon Hill/Boston Common/Public Garden hotels can offer the best location for those who enjoy exploring the city on foot. These include the Four Seasons, XV Beacon, and both Ritz-Carlton properties.

Boston's waterfront is not terribly appealing or developed, unfortunately. However, if you like waterfront views, the Marriott & Boston Harbor hotels have them, and both are close to the Quincy Market (undistinguished-but-popular restaurants and shopping) and Aquarium.