Apple iPod! By far. There are some outright strange things about the Sony app like not being able to manage a queue of songs easily without creating an adhoc playlist, the navigation is sometimes frustrating, and the default desktop app they provide to sync songs to the player in a manner that will keep lyrics and song art intact is absolutely atrocious. But pretty much everything else is good and there's nothing else on the market so...
Can you recommend an audio player with a better UX than the default Sony app?