| Marco,
I had a decapitated bass by checking my bass as luggage, in a crappy canvas bag. The insurance money worked out pretty well for me, but it was traumatic nonetheless.
I think whether there's a passenger-accessible area in each car depends on whether you're east or west of Chicago--if I remember the western cars are double-deckers and have those storage areas available, but I don't think the eastern ones do.
If I had to do it again, I would probably opt for the hard case, and at least attempt to store it myself rather than check it.
-Jeff | 
