I bought an S&S coupled Co-Motion single road bike in 1998 and sold it in 2012. I bought it when I was traveling for business a fair bit and it accompanied me to England, Japan and Italy and a couple of domestic cities on several trips.
What prompted me to sell it was retirement and the fact that airlines no longer accepted the hard case (or anything else) as free checked baggage.
My likes and dislikes mirror yours:
Likes: No oversize baggage charges, the case fit in taxi trunks and train luggage racks, once assembled you had no indication it wasn't a regular full size bike.
Dislikes: Disassembly and reassembly were a bit laborious and time consuming and not for the faint of mechanical skills, the old-style the hard case was awkward to wheel around airports, etc. (the newer ones are better), these days having to pay to check any domestic luggage removes some of the incentive, the hard case was easy to store in hotel rooms for local riding or a loop route but would be a real hinderance for a point-to-point trip.