JBL 15G firmware got posted today (
http://jetbook.net/upgrade.php) but the instructions have not been updated. The process is the same EXCEPT now you start with a freshly formatted FAT SD card (not FAT 32) like before, but copy over the folder named Firmware (only). There is no Data folder and no Reflash NOR folder anymore. It must not need the other two folders because my reflash was successful.
I don't know what improvements this upgrade does yet, and of course, since Ectaco is one of the last software companies in the world that does not believe in release notes or that the customer has a need to know, we will be left to discover the features ourselves.