I've used soft cases quite a bit for traveling with both my S&S single bike and tandem, never any trouble. You can fit more in them, especially since there are big outside pockets you can stuff with clothes and other soft gear (indeed, it's part of the design to provide padding for the contents). It's also a good bit lighter than the hard case, which is important in these days of 50 pound checked bag limits.
You could ride with it, but it's not so easy. The bag weighs about 7-8 pounds (from memory). The bigger issue is the side stiffeners, which are 26" long (and there are four of them), so that will take up a lot of rack space and be awkward to carry. I did bring my case along once on a short tour, but I didn't bring the stiffeners. I was returning on AMTRAK and was hand-carrying the bag so I didn't worry too much about padding and the stiffeners (see the page on my C&O tour journal where I talk about it at http://www.crazyguyonabike.com/doc/p...id=178345&v=35
the ever shifting stable loaded with comfortable road bikes and city and winter bikes
For Euro or US train travel perhaps, but its a little less than ideal.
I worked with some world class bike polo players that travel all over, totally endorsing the soft cases for their Bilenky S&S polo bikes (Go Dusty!). They also ride singlespeed bikes, and don't mind if they are beat up.
I met a bike tourist that combined trains and the soft case for regional trips. it was a huge bundle on top of his rack. Certainly viable. He LOVED it, absolutely LOVED it.
I've used my S&S bike with the hard case so far, but for a point to point tour i would likely use the make a cardboard box method.