No biggi just two new visualizations.And support for TV and Movie service.
Here:
http://www.pspfanboy.com/2008/07/14/firmware-4-05-features-hidden-support-for-movie-and-tv-service/
http://www.pspfanboy.com/2008/07/13/firmware-4-05-will-have-new-music-playback-visualizers/
Link:
http://pspslimhacks.com/index.php?dl_id=110
Here:
http://www.pspfanboy.com/2008/07/14/firmware-4-05-features-hidden-support-for-movie-and-tv-service/
http://www.pspfanboy.com/2008/07/13/firmware-4-05-will-have-new-music-playback-visualizers/
Link:
http://pspslimhacks.com/index.php?dl_id=110