Matt Yglesias and John Schwenkler have a great couple of posts (here, and here) on the relative advantages of buses to rail.
I must say that my experience with buses has been pretty pleasant thus far. I took the bus from Braddock Rd to the Pentagon at least once a week this past spring, and never had a bad experience.
The closest I came was this one time when a crazy old guy jacked up some nerdy bureaucrat for being too loquacious while he was trying to sleep. It was pretty amazing. As the great Walter E. Williams once said, there a number of ways of resolving conflict. In fact, violence is such an effective remedy that the government sees the need to monopolize it.
Anyway, back to the buses, why should they be financed publicly? The usual answer to this question is access. I don't buy it - even with expensive gas. I can't help but think of the amazing competition for riders from Washington to New York. Here, here, here, here, and here just to name a few. These offer leather seats, free wireless, etc. for as low as $20 one way and $35 round trip. Some even had limited-time offers for free one-way trips.
You would never see any of these things in a government financed mode of transportation. Competition is the very thing that disappears due to the crowding-out effect of public financing, and this is why costs never come down.