All nice and well, but A) it worked for me on iTunes 11 (up till 11.1.2) on OS X Mountain Lion (10.8), yet doesn't on Mavericks (10.9). Neither for my iPhones, nor for my iPad… So I really do believe that it IS a Mavericks related issue, even though it might not be known yet. Luckily for me, I don't sync quite that often, but I can only imagine it's a real pain in the proverbial backside for those who do…
FYI: I'm on OS X 10.9 (General Release).