Figured out what the problem was. As others have reported, need to plug into the main USB port rather than the keyboard ones the imac has. Worked immediately. Bummer you can only transfer media files. Would love to get pdfs on there.
In order for this to sync with your Mac, you have to go to settings --> applications --> and untick USB debugging. After unticking USB debugging mode, open Kies Beta, connect USB with your SGT 10.1 and should connect. I hate this Kies software. Very buggy. This is Samsung version of Itunes. wack!