I commuted to Boston for three years and if you have to do it, the train is far and away the best way to go. The few times I had to drive in rush hour it took me over two hours to get to the Back Bay, vs. a pretty darn consistent 55 minutes by train. Also, because Providence is the first stop you can usually get the coveted table seats on the double-decker trains, but be prepared to socialize.
Now, I had a pretty perfect setup, since I could walk to Providence station and my office was a block from Back Bay station so that definitely contributed to making the train work for me.
Just the same, I was very glad to stop commuting and get those hours back, but for a while the train was my third place (and if you don't get the reference from "The Great Good Place", well, that's for a different post).