XNJB is a great program and is highly recommended. I was able to download a 1.2 gig file from my new (refurbished) JB3 to my G4 iBook running OS X on Sunday night using version 0.21
and it worked fine but took a long time using USB 1.0. I had tried earlier using version 0.2 but it continued to crash at about 250mb.
Kudos to Richard for the fine work.