I have to admit a bit of a bias - but I think some of the best cycling (though lots of climbing) in Massachusetts is a bit south of your proposed route. Between Wachusett Reservoir to Quabbin Reservoir, a stay in Amherst or North Hampton, then through Savoy Forest to Adams. From Adams, if you are in a hurry head to Pittsfield, but if you have an extra day, heading up to North Adams and spend time at MASS MOCA - it's well worth the diversion. (Or, if you *REALLY* love to climb, head up Mt. Greylock.)
-mr. bill