It's 38 minutes to the 128 station, which is hardly Boston proper. It's an hour between Providence and Boston (South station), and the cost difference between the commuter rail or even Amtrak regional with the Acela is crazy. $12 MBTA train vs $16 Amtrak regional vs $50-$80 or more for the Acela. For what amounts to a 5-10 minute savings.
Looks like it depends on direction. Southbound trips are scheduled for 38 minutes from S. Station to Providence, but around an hour going north. MBTA is currently $11.50 each way. Amtrak is $.50 more if you buy two weeks in advance.
