The files are stored in the SD card using the FAT16 filesystem, so it is compatible with almost any PC. You can easily transfer any file from a computer to the card (in root directory only), but first you have to format this card with that Filesystem.
The long file names are supported, but a limit is imposed by the following define, located in FAT16.h: The hot-plug feature allow you to insert and remove the SD card whenever you want while the device is turned on.