I'm shocked that I'm typing this, but "yes", the best meal I've ever had on Amtrak (other than what the chef used to make just for the crews) is the Chipotle Veggie Black Bean Burger.
I'm no vegan, but man, that menu item, prepared properly, (not sitting under a heat lamp for a long time) truly is tasty.
The steaks have always been so-so, nothing ever close to real steakhouse, same for crab cakes. (hey, I do live in Maryland, so I'm a bit prejudiced) I have to also agree with the salmon and the buffalo, pretty darn tasty.
In my opinion, breakfast has slipped the furthest on Amtrak. Removal of the toasters, (no English muffins, no toast) hardly ever find eggs cooked to order, but they RARELY screw up the grits!