After 39 years of cycling and with 7 bikes already in my garage (3 are my wife's), I've joined the foldies. During the course of my internet research, it appeared to me that the number 1 motivation for going to a folder is the need for space, in a small appartment (I've got a two car garage with only one car), car trunk (I've got a mini-van with no rear seats), or even in over-the-road truck cabs (good for them). The number 2 selling point seemed to be for commuting - unfold, bike to public transit, fold, ride, unfold, bike to work, fold, store at work, and repeat the process in reverse (I'm retired). So that leaves number 3 - travel, in my case Amtrak (despite its problems, it's the only civilized way to travel, outside of bike touring, of course).
Although I've been all over the country with my bike on Amtrak, unfortunately there are a lot of city pairs for which bike carriage is impossible. My son and daughter live in Denver, but unfortunately the California Zephyr has no baggage service, required for bikes on that train, between Chicago and Omaha, much less near where I live. So I bought a used bike to store there. My other daughter lives in Santa Fe; but again no baggage service on the Southwest Chief between Chicago and KC. So I drive (ugh!). I've bicycled the Great Allegheny Passage and C&O Canal between Pittsburgh and DC with no problems since the Capitol Limited has baggage service at both end points. However, although the train follows the bike path almost the entire way, there is no baggage service between the train end points; so that leaves out starting or finished the ride in Connellsville, Cumberland, Shepardstown, or Harpers Ferry.
I could go on; but to make a long story short I had folders in the back of my mind for a long time, thinking I could hide it in a sack and bootleg it onto any train. I often bragged that I knew more about Amtrak and bicycles than 75% of Amtrak employees; but I wasn't as smart as I thought. Lo and behold, someone over at the Amtrak Unlimited forum pointed out that folders count as carry on luggage, which is great because, unlike airplanes, railroad cars have plenty of baggage space. That was all it took to make plunge, in my case a Dahon Mu p8.
Welcome! I like train travel, too, and agree that it's a great way to go. It's too bad so many of the Amtrak trains don't allow bikes (other than folders). I wonder if there are any cycling clubs or other organizations pressuring them to change that policy.