When I bought my Lumia 920 a few days ago I was very concerned about being able to sync all my iTunes music to the device efficiently (including purchases and playlists). After fooling around with the Windows Phone desktop program (which couldn't copy my playlists, and crashed numerous times during sync), I was quite disheartened and almost ready to take the phone back. I didn't want to go to the iPhone 5 cause I really like the WP8 interface and love the Lumia. I did some digging online and found a program called DoubleTwist. The program emulates the iTunes interface and works similarly. It imported my iTunes playlists and content right away (even though my music is quite fragmented, located in a few different places on my hard drive). It recognized my Lumia right away (even quicker than the Windows app). The program froze up the first couple of times I tried to do a sync, and missed some songs. After rebooting the computer and phone, I was able to get through a full sync and all my iTunes music including playlists and purchased content is now on my Lumia. This is not a perfect solution as the program doesn't work as well as iTunes, but it is a good program to hold you over until Microsoft develops a proper music management program on the desktop end that is somewhat friendly with iTunes. Hope this helps!

PS I found DoubleTwist works better if you launch the program, wait for it to load the iTunes/WMP library and then plug in your phone and sync.