musicdrv_opts=mp3_brute_mode=off mp3_use_me=on mp3_check_crc=off mp3_buffered_io=off mp3_buffer_size=65536 wma_buffered_io=off wma_buffer_size=65536 show_encoder_msg=off

^ You mean that?  Tried changing the two values from 64K to 1M and *_buffered_io to on, and MP3s definitely do play better (though fastforward/rewind is still a little dodgy).
Unfortunately, as the name suggests, it only affects MP3/WMA, and doesn't help with AAC, OGG & FLAC unfortunately :/  Also tried manually adding stuff like ogg_buffer_size=1048576 ogg_buffered_io=on but it doesn't seem to respect those.

After using this for a while, it appears there's no ability to delete everything in the playlist (you have to do it one by one).  Kinda annoying when you want to make a playlist of a folder, then scrap the playlist and make it from another folder - you have to manually delete everything in the current playlist first.  Not sure if deleting the music.lst file is a shortcut for this, but it's still a little annoying.