I have an older Archos Jukebox Multimedia with a 20Gb HD. It came with an adapter to transfer files from a CF card to its hard drive. I have used it to transfer data files and it has worked quite well.
I'm curious about using it for field transfers of photos. The transfers were painless - basically choose a folder and press transfer.
I'll give it a try in the next few days. If nothing else, it is more convenient than carrying a laptop while hiking, although having a few CF cards or microdisks would probably be better.
The biggest problem has been its battery life. About 3 hours of operation and they can't be replaced, only recharged.