Get a car as soon as you can, and try to stay away from the bus services. Once you have done that, you should be fine driving to school, leaving town on weekends, and giving the less-fortunate first-year students rides to wherever you are going. Driving to Williamstown is pleasant, not confusing, and the roads are good even when you get 30 inches of snow.
As far as flying goes, nobody has an easy time driving to the major airports in cities like Boston or New York, and the College has done a fair bit to accommodate students who come from those cities by providing a regular, reliable, and relatively cheap shuttle service. While people say that Williams is in the middle of nowhere, the availability of transportation options is not at all discouraging. The College even hires drivers who pick people up from major airports at fairly cheaper prices than most car services would.