Figured this deserved its own discussion thread.
The way the PlaylistEntry code is now set up seems a little less than ideal,
as readPropertiesThread and readMetadataThread assume that they are being
called from a non-main thread. This doesn't seem like a very modular design.
What about moving this code out to PlaylistLoader and using NSOperation from
there? There should be a better thread-safe way of dealing with the
inability to retrieve properties for a file.