Want to see your Zune from your Mac? You can.
But that’s about as far as you’re going to get. So far.
The Zune will not allow non-host computers to download data off the unit. Yes, I’ve followed the Zune Boards hack and have been able to transfer data onto (and off of) my Zune. You trick the Zune into lowering its non-transfer security gates during a sync and then access the Zune as an external disk during the sync. (Hint: transfer a TV episode in MPEG-4 format. It takes a good long while for the video to convert to native WMV and then copy to the Zune.)
But that won’t work with the Mac, because the Zune treats all computers other than the original host as hostile entities and will not allow access to the Zune data without a total reformat/rehost.
Clearly, the trick will lie in telling the Zune that it’s attached to a host and then pretending to “sync”. For now, XNJB allows you to see the contents of the Zune but all transfer attempts fail.