The Springfield shuttle is doing fine, especially after Amtrak increased departures/arrivals to eight a day last May. The only problem with it is the schedule is grossly padded.
It is scheduled for 1 hour and 20 minutes (most of the time). A few weeks ago, the 4:05 pm leaving Springfield left 20 minutes late and was scheduled to arrive in New Haven at 5:30 pm. The Springfield had to make the Boston connection--and there was not much room for error on this train to make the connection. However, the crew appeared to have made sure--made damn sure--that the train got to New Haven in a hurry. Lo and behold, the train arrived in New Haven at a a minute or two before 5:35 pm and made up more than 15 minutes on a scheduled 1 hour and 25 minute ride!!
It is a pity, if the rider has perception the that they are going faster than a car, they would get more ridership. This is also an issue between New Haven-New Rochelle (especially as I look out the window and see the cars zipping by on I-95), but I realize this is more of an issue with Metro-North.