I use a NW-ZX2 with a Mac.
I created a new, additional iTunes library on the Mac, pointing the iTunes Preferences --> Advanced location of the iTunes media folder to the MUSIC folder of the Walkman.
That way, I can edit all the metadata for the music on the Walkman using iTunes.
(To create an additional iTunes library, hold down the Option key when you start iTunes. It will ask you if you want to create a new library. Do that, and name it "iTunes Walkman." While you are working on your Walkman's internal storage use that library. When you are done, quit iTunes, and again restart with the Option key, and choose to use an existing library, namely the main default iTunes library on your Mac.)
I also made yet another iTunes library for the SD card in the Walkman.
This makes it much easier to edit metadata, add art and just plain see what is on your Walkman and on your SD card.
I don't use Playlists so I don't know whether any playlist made with iTunes will be detected by the Walkman, but would love to hear from anyone who tries out my method.