The one reason I haven't bought a new Sony Ericsson phone is that there is no software supporting OGG files for those phones. I have encoded all my music to OGG format for playing on my Nokia 6681 on which I have installed OggPlay.
I would love it if this software were to be ported to support SonyEriccson Walkman series phones.
I am sure there are many who would agree with me.
In case I am mistaken, and there IS a way to listen to OGG music on a SE phone, please let me know. :)