Back in 2002 or so, I had a bicycle retrofitted with S&S couplers.  These allow the frame to be split into two pieces and disassembled into a small enough package to escape oversized baggage charges for air travel.  While this sounded like a great concept at the time, in practice assembly and disassembly time each take at least one hour (you can see photos of my packing sequence here).  Two hours of overhead is quite considerable when taking into account that the main purpose of the retrofit was for me to take the bike on short plane trips.

I’ve found a couple of other blog posts that share this point of view:

http://piaw.blogspot.com/2006/09/ss-couplers-revisited.html

http://piaw.blogspot.com/2005/08/ss-couplers.html

He gives a few good reasons where couplers are most useful – but on the other hand, a folding bicycle would also be suitable for most of those applications.

I can think of a few other applications where the couplers would be useful:

• Long duration (2+ week) bicycle tours, where one would want the comfort/handling of a full sized bike instead of a folding bicycle (where the long trip duration offsets the unpacking/packing time)
• Triplets (three-seated) or other specialty bicycles, where due to its size, the bicycle needs to be partially disassembled to fit in a car or to be transported by other means
• Related to the above, there are some tandem manufacturers that make bikes that convert between a two-seated and a three-seated tandem, for which the couplers are used to add or remove the middle section of the bike.

Since none of these are going to happen anytime soon, my current solution is a folding road bike, a Bike Friday Pocket Rocket.