That is not entirely correct. I have several years working on iSeries as well, but only using Windows clients.
FTP maybe a standard, but some FTP clients do not recognize the AS/400 file system when retrieving the directory/file list. Viscom just confirmed that the Mac version of their FTP client does not support the AS/400, and Peter Lewis, the developer of Interarchy, has also confirmed this.
Using a client on Windows like WS FTP Pro, I can browse the AS/400 structure easily. I have Security Officer privileges, which is the highest level. There is something about the clients I've tested (other than Transmit) that when they attempt to retrieve a file list from the AS/400, it doesn't display, so I was looking for other suggestions.
Symtex, what do you use when you need to download a file from your AS/400?