A function to search for duplicates has been added (Database->Find Duplicate Tracks... menu). You can choose which fields should be considered in the search.
An new release of Music Box is available: libvorbis has been updated to version 1.2.0 to avoid possible security problems which have been discovered in the previous version.
This version can read tags from protected AAC files (the ones you can buy on iTunes Store).
The Composer field has been added to the track properties: it's useful especially for organizing classical music. The ID3v2, Ogg Vorbis and Monkey's Audio parsers have been updated to read/write it.
Last but not least, you can now export tracks in the .m3u playlist format.