Boston public transport is beautiful, really. Rhode Island is pretty good too - the buses are common and fairly frequent, and they have a train that goes to Boston for cheap.
The train that goes to Boston isn't an RI thing; it's an MBTA train. Not sure what allows that set-up politically or whatever.
Public transit in RI really, really depends on where you live. I used to live about 25 minutes from college by car. By bus, I would first have to walk a half-hour to the bus stop (you aren't likely to have a very close bus stop unless you live in certain areas), ride the bus for another 40 minutes or so to Providence, and wait at the bus depot/plaza downtime for a variable length of time to catch another bus. The shortest bus from Providence to college (that last mentioned leg of the trip) used to take about 35-45 minutes as well, but a route was changed so the shortest one is now more like 20-25 minutes. So instead of a 25-minute ride, I had anywhere between a 90 and 130-or-so minute Magical Public Transit Journey. Oh, and that half-hour walk to the bus stop? For a decent length of it, it's along a fairly busy road with no streetlights or sidewalk, and a few curves, and drivers were not terribly careful. This was pretty dangerous at night, basically impossible after a heavy snow, and was mostly uphill on the way there... and not any easier while carrying a load of schoolbooks and/or a laptop.
This is neglecting to mention the fact that the public bus system has its fair share of creeps and Things Which Inexplicably Smell Like Things They Should Not.
So yeah, it really, really depends on where you live. Some places in RI, the bus system is extremely convenient, and in some places it's completely inaccessible. At the time, I lived in between those two extremes.