Not sure what you would define as a "long trip" but I've taken Amtrak a couple of times up to South Kingstown, RI to see friends over the past few years.
I lived in Rhode Island for 4 years and made the trip up and down the disaster that is Route 95 in Connecticut way too many times. Took other routes as well, but Southern CT just is awful for traffic.
So I decided to take a flyer one time on Amtrak from Metropark to RI. Gotta be honest, it was pretty pleasant. I brought lunch, a couple of mixed drinks in insulated containers and listened to music and read. Was nothing like riding on NJ Transit, at least in my experiences. Train was quiet and it was much less stressful than that commute I always made back and forth from RI to NJ.
Now that was only about a 4 hour ride, so I'm not sure how far you are looking to go. But in my handful of times taking this route, I found it to be ok for me, traveling solo.