Transportation uber-geek Todd Litman looked at studies of people's satisfaction with their commutes (PDF). The results: transit isn't all that popular, compared with a car commute:

The leftmost bar represents a car-only commute; you can see that it gets higher satisfaction ratings (the green part) and lower dissatisfaction (the orange) than both transit and car+transit commutes, which are the next two bars. (Despite the popularity of park-and-rides, there are lots of yucky orange feelings towards a mixed commute.)
But, wait! If you dive into the numbers, it turns out there's another side to this story. As it turns out, people don't have an inherent preference for cars, or an innate dislike of buses or trains. The real story is that people don't particularly like spending time in vehicles, period.