I know itīs not relevant in this discussion, but wouldnīt it be possible to use the same coding that mdīs are using, ATRAC. It would raise the quality alot, I think. But then There is the problem that sony hardly wonīt relese the source or even build an encoder/decoder for an computer.
Because nobody would want to. ATRAC puts 74 minutes of music into roughly 175MB. I'm not sure about the bitrate, but it's 44khz, which is the same as most MP3s. But MP3 can put more than twice as much music into the same space, and at better quality. So, there's your answer. People don't want ATRAC on their computer because we've already got something a lot better, and it's free.