Does anyone have any experience with soft sided bike transport bags?

I was just reading a bike tour brochure & the tour company won't let you bring hardshell cases (like the trico iron case in the other "bike transport" post). They WILL let you bring your bike in a cardboard bike box (b/c it can be flattened for storage), or in one of the soft sided bags.

If I go, I'll be flying, so I would love to hear from anyone who has used the bags. What did you think? How did it compare to a hardshell case or the good old box?

Thanks!