Light the Halo (Geoff) often takes the train from LA to seattle and has posted on facebook how much he has enjoyed traveling that way.
my grandparents refused to fly so they always took the train from chicago to LA. they were convinced that every single plane was going to crash. they enjoyed traveling that way.
as others have mentioned, the ability to get up and move around and not be packed in tight like on a plane is a real nice benefit. i'd do a cross country train trip if i had the time. enjoy.