Ahead posted today the changes log from the previou v5.5.9.7. According to the log the main changes are... Bug Fixes:

Improved error message if a user tries to drag & drop ".cda" files from a recorder into an audio compilation
Improved support in Nero file browser for Arabic language
Improved support for *.iso images in Nero and NeroExpress
Fixed error message appeared sometimes during the shutdown of Windows XP directly after closing Nero
Fixed a bug in the verification procedure for DVD
Setting for boot disc compilation will now be memorized correctly
Fixed a multibyte CD-text problem on some Japanese systems
Corrected the name of the attribute column in the file browser
Enabled speed setting for DVD+R/RW writing and set write speed to minimum 2,4x
NeroExpress: Improved the fixation flag for Disc-At-Once and DAO/96 for some drives

New:
Added several new recorders
DVD recording is now compatible with X-Box " DVD players
Removed country flags from Nero language dialog
Nero supports now the NeroNET-Client functionality. This means that users are able to burn on the NeroNET servers somewhere in a local or remote network.
Added support for Nero Robo functionality in Nero and NeroExpress
Added new MPEG-4/AAC trial version. Limitation: 50 times encoding / 30 days decoding