Sonys brand new OLED walkman the NWZ-X1000 series are reviewed by Engadget.com
The Sony OLED Walkman boasts a 3 inch WQGA Amoled Display with 432x240 pixel.

Engadget about the OLED Display:
The OLED panel itself definitely lives up to the hype, but unfortunately we're not so sure a fancy display justifies the steep increase in price versus LCD-based rivals.

There are some great pictures which shows the X-series in comparison with Cowon S9, Ipod Touch, Samsung P3 mp3/mp4 players.

Sony Walkman X Series 32 GB Video MP3 Player w/ OLED Display