iTunes sync stuck on step 5: Importing Photos
Deleting ~/Pictures/iPod Photo Cache and emptying the trash did the trick for me. 

Just to be clear,


Quit itunes. 
Go to your home folder in the Finder
Go to the pictures folder
Right mouse click on "iPhoto Library.photolibrary" and choose Show Package Contents
Move "iPod Photo Cache" to the trash.
Empty the trash.
Open itunes and run a sync