I own four S&S backpack soft cases, and that's all I use anymore (I also have the hard case). I've posted elsewhere on the forums about packing strategies and whatnot, but I've found that as long as you use enough clothes as padding in the outside pockets you'll be fine. I've flown our tandem, triplet, and single bikes on multiple trans-atlantic flights with zero issues. All told, I probably have 40+ bag-segments flown with the backpack cases (when you consider two bags per tandem x each r/t flight = four bag-segments). In August we flew PHL-Munich-PHL with the triplet in two S&S cases, and last week I got back from 10 days in Germany with my Co-Motion single in one S&S case, flying in/out of FRA from PHL. So, in the past month alone I have six "segments" of use with the S&S backpack cases. I only mention that as a relevant data point. The only snafu was on the flight back last Sunday, where US Airways forgot to put my bike bag on the flight, and I didn't get it back until Tuesday morning. But it came through without any issues.
The one and only time I've had a problem with shipping an S&S bike is when I used the hard case. Somehow the case must have gotten a really good whack, as the drum for my Arai drum brake (cast aluminum) got cracked and I got a small dent in the downtube on my Santana tandem. As an aside, when packing the tandem or triplet, I pull the axle, cassette, and Arai pad assembly to reduce the protrusions in the rear wheel (dang Santana 160mm spacing causes packing challenges, for sure).
For my single bike, it took about 15 minutes to pack up for the return flight, and maybe 20 minutes to put together when I arrived (jet lag doesn't help). In addition to the wheels (obviously), I remove the wheel skewers, drive-side crank, handlebars, and rear derailleur. Padding is S&S Velcro and foam pipe insulation. The bike (Co-Motion OR 26" Co-Pilot) and all my clothes for 10 days went in the S&S case and I topped the scale at exactly 50 pounds. Extra stuff went in a carry-on bag.
Photo 1 below: Co-Motion OR single bike (26" flat bar bike) packed in S&S backpack case. Also in main part of case was my helmet, Ortlieb handlebar bag, Blackburn rear rack, some tools. In outside pockets were almost all my clothes for 10 days (including a week of work meetings). Case weighed exactly 50.0 pounds.
Photo 2: Our Santana Cabrio triplet and all our gear for 16 days in Europe this past August, including clothes for two adults and our seven-year-old son. The center section of the Cabrio is in the cardboard box on the bottom in a custom crate I created (see the
thread on making the crate) Most clothes went in the S&S backpack cases' outside pockets. We had two carry-ons as shown in the photo. All checked bags flew for free and were within the size and weight limits. At arrival, I collapsed the crate, one S&S case, and the two carry-on bags and put them in the second S&S case, which we stored at a hotel we were staying at on the last night of our trip near the airport.
