Also, you will have to uncheck the "compilation" setting in iTunes to get the songs to show up in SYNC, or such has been my experience. I only had about 8500 of my 10000 songs show up, so did some reading in various forums and that was the suggestion that helped me most.
I basically opened up my iTunes music directory folder and then went to Compilations. Anything in there, I brought up in iTunes and edited to not be a compilation. Sure, it makes it much harder to copy a single compilation album anywhere, but it does allow SYNC to find the songs.
I still have about 400 songs that it won't find, but I assume that is due to missing tag info... that's the next mission.