Part of my decision to buy a place in Gloucester steps from the commuter rail, was the fact that I knew in a short amount of time internet connectivity on trains would quickly be a reality. If you can spend your time commuting, working, guess what that means? You can get more accomplished in a day, or your work-day is shorter -- I'll take either. More often I use the time to catch up on email, news, and collect my thoughts.
For a while(last five years for me), internet access on the train was reserved for business people who either had a company sponsored cell-network card, or could afford to blow 60$ a month on the data plan -- or tech saavy guys like myself that tether their cellphone and use it as a modem (no cable, Bluetooth of course) without paying a hefty premium (I use my cellphones basic data plan, 6$ per month).
Now it looks like the MBTA is trying a pilot out, and from the looks of this graph of coverage on my line, I'd say pretty promising for the future --