>Booking well in advance is the only way to get a good rate, "walk up" prices are pretty high
In all fairness, that's pretty true in a lot of places. It certainly is in the UK in my experience. I'd actually have said at least the Acela isn't particularly onerous in this regard.
This was true in Denmark last I was there. You could buy an "orange" ticket online, well in advance, for a significant discount, which I used for a planned trip into Copenhagen from Jutland.
In all fairness, that's pretty true in a lot of places. It certainly is in the UK in my experience. I'd actually have said at least the Acela isn't particularly onerous in this regard.