Depending on where you live, driving is still the cheapest and fastest option, even with escalating gasoline prices. In my case, much of my business can be conducted over the cellphone on the drive to Montreal, which in my case is 6 hours. There are 2 caveats to this: (1) using a cellphone while driving becomes illegal in Connecticut effective October 1, 2005; (2) Generally you lose reception through the Vermont mountains, so in my case I get all my calls done before I leave Massachussetts.
I have taken Amtrak to Boston and Rhode Island. I find it kind of expensive so I have only used it for exclusive business related travel.
I am familiar with the station near the Hilton Bonaventure. It's nice that Amtrak takes you to that station. And Curious is right, once in Montreal downtown you really don't need a car.