You know, the thing about Daily Kos is that the "community" there discusses the intersection between politics and policy, and that they consider themselves the "reality-based community." Thus, if someone in that community wants to complain about Amtrak (even if the complaints are well justified), the complainer should take the time to look at the structural issues about why things are so crappy rather than just say the whole thing should be thrown out.
There are a number of policy issues involved here: (1) does passenger rail have a place in the US transportation system? And what is its place? (2) If passenger rail should be supported, should it be subsidized by the government? That second question is sort of silly, as all transportation is subsidized by the government. Perhaps the better question is what the form the government support should take. On the one hand, there seems to be this American myth that government agencies are incapable of doing anything right, though nobody is seriously suggesting (yet) that we should privatize the US Marine Corps, etc. On the other hand, there is a (well justified) aversion to shoveling taxpayer money into something that benefits a private corporation. Amtrak is something of a bastardized hybrid -- it's a private corporation in which the stock is owned by the US Government, or rather, "We the People."
If you believe that an well-integrated national passenger rail network is an important part of a well balanced transportation system (like I do), then this arrangement actually is a good way to funnel public subsidies into such a system. Whatever other shortcomings Amtrak has, I've never heard any accusations that the top brass are enriching themselves at the taxpayers' expense. It might be interesting to compare Mr. Boardman's total compensation with that of the CEO's and entrepreneur/owners of the various airlines, class I railroads, large-fleet trucking companies, etc. I really think that Amtrak management is probably more interested in trying to run a railroad than make as much money as they can, which is something you can't say about most privately owned companies.
As to whether passenger rail is relevant to most Americans, it seems to me that it's a major player in the urban Northeast and it is growing in the Chicago hinterlands and the west coast. And, come to think of it, commuter rail is a growth industry in Colorado and Texas, among other places.If you add up the population of those places, it adds up to a fairly large proportion of our Nation's citizenry. Certainly a larger portion of the citizenry than those who benefit from farm subsidies, for example.