The ONLY time I ever considered taking Amtrak was to go to NYC and stay in midtown Manhattan. The train from Boston goes into Penn Station right under Madison Square Garden(7th and 34th street). We still decided to drive from NH because it is over an hour drive to get to South Station in Boston. FYI, it costs about $45/day or more to park a car in Manhattan. It is over $100/day to park a Suburban.
So, even though I live near the I-95 corridor, the train only makes sense if you live near the train station.
A problem, though, for those living to the north is that trains going to Boston from Maine and New Hampshire go to North Station, while those leaving from Boston for NY and DC leave from South Station.
North-South rail link is something they've been talking about for years.
In my grandparents' day there was an elevated line between the two stations.