I've had an early-version Sloan "fold-a-jo' since the 1970s; used it for domestic and international travel. Mine was made by pappa Sloan, who I recall has since passed.
Deb Lamberton, who does programming for NPR, uses one, too. She introduced me to the f-a-j at one of the Brandywine Mountain Music Conventions and I did an article on them for The Folk Life, back when it was still in publication.
I really like mine for travel--it fits into a back pack for carry-on when flying, and you get the extra bonus of watching the airport screeners freak out when they see the metal pot and twisting assortment of strings on their screens.
Sound is good; play is easy. It takes nylon strings, so a richer tone than metal. I use mine for personal play and keeping up with practice; never tried it as a ensemble or performance instrument.
The new ones are more finished than mine and they strike me as a bit expensive; but they are uniquely useful for their particular task and worth it if you can afford one, I think.
Feel free to PM me for more details and for photos.