Gave this a shot - pretty good player, which does some things right where various other 3rd party PSP music players have gone wrong.
Some issues I've noticed (and perhaps suggestions):
- Fastforward/rewind is a bit quirky - the song continues to play, and it only jumps when you release the Left/Right d-pad key; an XMB style "fast playback" would be nice, but could be difficult to implement.  FF/RW not supported in AAC at all.  In OGG, it seems to stuff up the playback timer.
- HE-AAC tracks actually work, but it get the length of the song wrong (it halves it) - I'm guessing it uses sample rate to calculate length somewhere
- Sleep doesn't seem to work properly with me, but IDK whether it's an issue with this program or my dodgy PSP
- It seems that if you disable the title screen, it doesn't actually do that, but it does stop you from entering the settings menu
- There's a nice playlist save feature, but unfortunately, loading has to be done from the filebrowser; also can't specify a default location for the filebrowser it seems
- The default UI is a bit cramped - seem to be shoving in too much stuff that some of the text is difficult to read
- I don't use them, but the fullscreen visualisers look kinda pixelated :P

Otherwise, format support is obviously amazing.  It's playlist oriented like many other players, though I personally like a basic filebrowser type, but that's your taste I guess.
Controls are reasonable and it does its job.
Definitely something to look out for.

Thanks again for posting as well!