I successfully uploaded 23GB of music from my hard drive (after lots of waiting) to Ubuntu One except that only ~20 artists/albums are showing up correctly and the rest are 'unknown'. They are (almost) all mp3 files and the correct info shows up when loaded into a media player, including Rhythmbox and Banshee.
Thus, this is not a problem with the files themselves (info also shows up correctly under properties->audio in Nautilus) but rather a problem with U1. There seems to be other threads with this issue but no answers, except for the excuse: "Ubuntu One does not currently support m4a files" which is clearly not the issue. This is of particular concern for streaming to my iPhone since all the music is disorganized, which really defeats the whole purpose of the app.
I should note that most song titles are correct (except may contain a song number in front of them) which from what I understand is due to the fact that generally the file name is the song name. Any help with this is greatly appreciated.