I have tried both the media sync that is supposed to connect you with your itunes library. My biggeset thing with it is that it doesnt allow to sync the DRM'd songs in your library.
A program i saw on cnetv.com called doubletwist removes the DRM and sync's it over to my bb with no problem works great and has no problems, i highly recommend it, and best yet its free!!
the software link is below, it has to be legal since download.com has it doubletwist software downloads and reviews at Download.com
its the desktop one, the 2nd in the list