I've got 20Go music on my N900 and no issue with the media player

All my artist/album/covers/year are embedded in the mp3 files

Only thing: when in Artists view, it takes maybe 2 seconds to "create" the list, and after that the scroll is perfectly smooth. But you start at the end of the list, which is weird, maybe there is a bug signalled for that

Edit: the bug is here, vote for it
https://bugs.maemo.org/show_bug.cgi?id=5901