Suporta pois!
E isso já acontece desde o NW-HD3, que era de dísco-rígido de 20GB. Tive um HD5, o modelo seguinte, e também lia mp3 nativamente. Simplesmente não tinha leitura gapless com mp3. Tive um A1000 de 6GB e o meu irmão tem o A805 e também leêm mp3.
"Well for once Sony is actually doing what everyone has been telling them to do for months and is adding
native support for MP3 playback to the NW-HD3, the new version of their 20GB Network Walkman"
retirado daqui:
http://www.engadget.com/2004/11/30/new-sony-nw-hd3-network-walkman-supports-mp3/
"Audio support is better than with older Sony audio players; the NW-A805 will playback mp3, aac and wma files natively."
Em:
http://www.pcw.co.uk/personal-computer-world/hardware/2187913/sony-video-walkman-nw-a805